For months, we've been talking about two different successors to the iPhone 5, including a true sequel with all the bells and whistles -- the iPhone 5S -- and an all-new design said to aim specifically at emerging and lower-income global markets like India and China. But to build this cheaper, more affordable "iPhone 6," one analyst believes Apple (NASDAQ:APPL) will release the phone without a Retina display.

On Friday, RBC Capital Markets analyst Amit Daryanani released a research note (via MacRumors) saying he believes the low-cost iPhone 6 will see its release date in June or July 2013, but the phone will not feature Apple's signature Retina display.

"Our supply-chain checks indicate that AAPL is working to launch multiple new phones in the June/July time-frame this year," Daryanani said. "Specifically, AAPL will launch the iPhone 5S and a more affordable but lower-income iPhone at the same time, in either late CYQ2 or Q3. The low-end iPhone will have the same 4" form factor as the iPhone 5 but will have plastic casing and no retina display [sic]. With a lower price-point, AAPL will be able to target a growing and important part of the Smartphone market (sub-$400 price-band)."

Several other analysts have said the iPhone 5S and iPhone 6 will both be released simultaneously in 2013, but Daryanani's note about the device's Retina display conflicts with other trusted reports from analysts who have proved accurate in the past. Specifically, KGI Securities analyst Ming-Chi Kuo, who correctly predicted Apple's entire product pipeline in 2012, believes the iPhone 6 will indeed release in June or July, but will feature the same 326 ppi Retina display as the iPhone 5.

It would make little sense for Apple to introduce an inferior display in the iPhone 6. Even the iPhone 4, which is currently available for free in the U.S. (with a two-year contract), features a Retina display. If Apple wants to lower prices, reducing the screen density won't make much of a difference in overall cost. Instead, it's been reported that Apple will build the phone with different materials, opting for a "hybrid casing of fiberglass and plastic" that makes it lighter and slimmer than most plastic-encased smartphones, but certainly cheaper to make. KGI Securities' Kuo believes the iPhone 6 will still be heavier than the iPhone 5S, which will reportedly be cased in aluminum and released around the same time.

Need more reasons to believe the cheaper iPhone 6 will feature a Retina display? On Thursday, Apple officially told developers that all apps submitted to the App Store must support the Retina display resolution (326 ppi) and 4-inch screen size of the iPhone 5 and fifth-generation iPod touch starting May 1. If all developers are being forced to scale their apps to the new screen size in May, Apple will likely make a big iPhone and/or iOS-related announcement soon after -- most likely at its Worldwide Developers Conference in June.

Why Apple Should Release The iPhone 6 In 2013

Apple is facing stiffening competition from its rivals at Samsung Electronics (KRX:005935), Google (NASDAQ:GOOG), and even Microsoft (NASDAQ:MSFT); recently, Apple got to see Samsung release its newest flagship phone, the Galaxy S4, which looks to be the biggest competition to the iPhone in 2013 -- like 2012 all over again. Apple will need all the firepower it can muster in its smartphone line-up if it hopes to maintain customer interest in a tightening marketplace.

With the advent of cheaper, smaller, and more power-efficient chipsets, Apple can certainly afford to build an entry-level smartphone in addition to its current iPhone 5 (or 5S) -- either making it larger, like the Samsung Galaxy S3, or possibly a smaller iPhone Nano -- to appeal to consumers who can’t quite afford Apple’s most popular product, including many in China.

Reports of Apple's desire to build multiple iPhone models have been echoed on Wall Street. On Jan. 2, Topeka Capital Markets analyst Brian White said the company will likely release its iPhone 5 successor in more colors and screen sizes, implying that Apple might sell an iPhone that's smaller or larger than the current iPhone 5 or even the previous-generation iPhone 4S or 4 units.

"Although Apple offers a 4-inch screen on the iPhone 5 and a 3.5-inch screen on the iPhone 4S and iPhone 4, the company has never offered multiple screen sizes for a single model," White said. "We believe this is about to change with the next iPhone offering different screen sizes that we believe will allow Apple to better bifurcate the market and expand its reach."

China is the biggest new market for Apple at this moment: The company is reportedly trying to strike a deal in 2013 with China Mobile Ltd. (NYSE:CHL), the largest telecommunications carrier in the world with 703 million active subscribers, to build a TD-LTE version of the iPhone 5 to work on the carrier’s high-speed networks. Apple CEO Tim Cook even visited China Mobile headquarters on Jan. 10 to meet with company Chairman Xi Guohua to discuss “matters of cooperation,” but Apple needs this deal now: The Samsung Galaxy S4 will release on TD-LTE this year, which presents an enormous opportunity for Samsung if it can release its popular smartphone unopposed.

Considering Apple’s urgency to strike a deal with China Mobile, as well as the growing competition to be compatible with China's most popular carrier, it’s likely we could see Apple release both the iPhone 5S and iPhone 6 this year in an attempt to dominate the growing markets in Asia.

iPhone 6 Rumors: What Features Might It Include?

iLounge editor-in-chief Jeremy Horwitz detailed in January what he called the "budget iPhone 5," which he said looks like the iPhone 5, but features several new design tweaks.

“Yes, it will be made substantially from plastic,” Horwitz wrote, echoing an earlier DigiTimes report that said the iPhone 5S or 6 would feature a hybrid chassis made of both plastic and metal. “No, it won’t just be a Retina- and Lightning-equipped refresh of the iPhone 3G or 3GS, Apple’s last plastic iPhones, nor will it look just like an all-plastic version of the iPhone 5. This new model is actually a cross between the iPhone 5, the fifth-generation iPod touch, and -- wait for it -- the iPod classic. Yes, really. It will have a 4-inch screen, like the iPhone 5, a bottom like the latest iPod touch and a shape that’s most similar to the iPod classic.”

The original DigiTimes report on the low-cost iPhone 6 said the new iPhone’s internal parts could “be seen from the outside through a special design." If this rumor is accurate, the finished design for the cheap iPhone 6 might look like an iPhone 5 mixed with the plastic enclosure of the iPhone 3GS from 2009 mixed with the final design for the Bondi blue iMac in 1998, which was characterized by its brightly colored, translucent plastic casing that could let users see the innards of their desktop computers for the first time.

Horwitz believes the low-cost iPhone 6 will feature specs nearly identical to those in the iPhone 5, but will be "a half-millimeter taller and a half-millimeter wider," as well as a full millimeter thicker. While these changes are minimal, Horwitz noted the biggest design change in the iPhone 6 will be the curves.

“Apple’s budget housing looks closest to the iPod classic in shape, though not in materials,” Horwitz said. “Unlike the plastic iPhone 3G/3GS, which featured soft curves on all sides, the budget iPhone’s curves start and end at flat surfaces, so each side and the back are flat. This seems like a trivial change, until you realize that it allows Apple to use flat rather than curve-matched parts: The right side has a flat, centered SIM card tray just like the iPhone 5’s, while all of the buttons and ports are on flat rather than curved surfaces. A flat-backed iPhone won’t rock on a flat surface when it vibrates, either.”

The proportions of the iPhone 6 will resemble those of the latest-generation iPod touch, with similar locations for the camera, microphone and rear flash, according to Horwitz. The bottom microphone, headphone jack, Lightning dock, and speaker are in the same locations as in the iPhone 5, but the new iPhone 6 is said to have an extra microphone on the bottom, as well as four individual holes for the speaker grill, rather than the 26 speaker holes at the bottom of the iPhone 5.

“In summary, the budget iPhone will look a lot like an iPhone 5 from the front, an iPod classic from the side, and an iPod touch 5G on the bottom -- only made from plastic rather than glass or metal,” Horwitz concluded. “It won’t make any bold departures from past Apple designs, but then, it’s supposed to be an inexpensive iPhone and achieves that goal pretty much as expected.”

Besides the form factor, Horwitz believes the next iPhone will feature a processor bump -- possibly an Apple-built A7 chip -- as well as improvements to the camera and flash, integrating a new aperture and 13-megapixel lens.

That said, most rumors about the iPhone 6 have revolved around its display, as Apple is reportedly investing a great deal of time, energy and capital on the screen for its next-gen iPhone 5S and iPhone 6.

A Jan. 3 report by the China Times said Apple might switch to a "Touch On Display" panel currently in development at one of the company's suppliers, Taiwan-based Innolux Corp. (TPE:3481), which has reportedly licensed Sharp's proprietary IGZO display technology.

Whether or not Apple taps Innolux to make screens for the next iPhone, however, the company will most likely feature Sharp's ultrathin IGZO display technology in its next iPhone -- the iPhone 5S, iPhone 6, or both.

In late December, Asymco analyst Horace Dediu and DigiTimes both mentioned Apple’s alleged investment in the ultrathin IGZO displays produced by Sharp, predicting the inclusion of the technology in Apple’s next batch of iOS devices, including iPhones and iPads. Dediu also pointed to Apple’s recent $2.3 billion investment in “product tooling, manufacturing process equipment, and infrastructure,” believing the cash was used to help bail out Sharp, which had been in financial straits last year. Sharp is reportedly going “all in” on IGZO technology, so it’s possible Apple saved Sharp to leverage its investment in the next generation of displays.

As noted by Tom's Hardware, the IGZO display is not only thin and tough, but also can handle even higher screen densities than Apple’s Retina display, which is visually stunning on its own. IGZO displays can reportedly handle display densities north of 330 ppi: In comparison, the new iPad 4 can only achieve 264 ppi.

One of the advantages of IGZO display technology is its lower power consumption. Most Apple products, from the iPhone 5 to the iPad 4, require cartoonishly big batteries to achieve just eight hours of power -- this is because current-gen Retina displays are extremely power-hungry. If Apple wanted its iPhone 6 not only to last longer during the day but also to charge faster when plugged in, IGZO seems to be the way to go for the next generation of iOS devices.

Apple sold 47.8 million iPhones and 22.9 million iPads in the company's fiscal first quarter ended Dec. 29.