The iPhone 5S hasn't been unveiled yet, but already consumers are pining for Apple's other iPhone 5 sequel, known informally as the "iPhone 6," which may be released alongside the iPhone 5S in late summer or early fall 2013.

Unlike the iPhone 5S, which is rumored to include a number of nifty security features thanks to the phone's alleged fingerprint sensor, the allegedly low-cost iPhone 6 is said to be specifically aimed at emerging markets for consumers who can't easily afford the high-end iPhone 5 or iPhone 5S. Besides adopting a new hybrid plastic-and-metal chassis, the iPhone 6 may also come with a flexible display to accommodate a broad range of hand shapes and sizes.

In a manner similar to how Apple re-engineered its EarPods in late 2012 to conform to the unique shape of the human ear, flexible displays can sustain a greater diversity of hand types, letting users grip, squeeze and contort their smartphones to their liking. The new phones are rumored to include a number of functional, gesture-based applications, too.

In one of its patents that was released last week, Apple describes how a flexible display could be functional in the iPhone 6:

"User interface components may be configured to sense inactive deformations of the device (e.g., a folded or open position of the device) or may be configured to detect active deformations of the device (e.g., active twisting, squeezing, bending or otherwise active deforming) of the device," the application said.

"User interface components may be configured to initiate a response from the device to the detected twist such as turning the device on or off, entering active or standby mode, answering a cellular telephone call, starting a software application, changing a volume associated with audio or video playback of media, starting or stopping audio playback of media, etc. For example, twisting a flexible electronic device may change the operating mode of the device, may be interpreted by the device as a command to an electronic gaming system, may turn the device on or off, etc."

Apple is almost definitely investigating flexible displays for future iOS devices. Earlier this month, Apple posted a job listing for a "Senior Optical Engineer" to "lead the investigation on emerging display technologies such as high optical efficiency LCD, AMOLED and flexible display to improve overall display optical performance."

Apple is looking for display specialists to "analyze the trade-offs between design, process, optical performance, and implementation feasibility," who have an in-depth understanding of "color and white point management, gamma and dimming control, visual performance and artifacts; and characterization metrics."

The job listing, which has been removed from the Apple website, could relate to Apple's heavily-rumored iWatch. But we did notice that Apple removed the job listing the same day it released more patents for flexible displays, all of which are designed for smartphones, not tablets or wristwatches.

Apple may be using Corning to manufacture flexible displays for its iPhone 6. Corning, which makes the ultra-rugged Gorilla Glass for the current iPhone and many competing smartphones, unveiled its thin, flexible Willow Glass earlier this year.

“Corning Willow Glass will help enable thin, light and cost-efficient applications, including today’s slim displays and the smart surfaces of the future,” Corning said on its website. “It will support thinner backplanes and color filters for both Organic Light Emitting Diodes (OLED) and liquid crystal displays (LCD) in high performance, portable devices such as smart phones, tablets and notebook computers. This new, ultra-slim flexible glass will also help develop conformable (curved) displays for immersive viewing or mounting on nonflat surfaces.”

Flexible displays could be a simple but powerful transition for Apple's iPhone. With stiffening competition from rivals at Samsung Electronics Co. Ltd. (KRX:005935), Google Inc. (NASDAQ:GOOG) and even Microsoft Corp. (NASDAQ:MSFT), Apple needs to establish a more intimate connection with its consumer base if it hopes to keep its dominant position in an increasingly crowded mobile marketplace. Between rumors of flexible displays and a transparent back similar to 1998's Bondi blue iMac, the iPhone 6 might end up being the most appealing, intimate smartphone released by Apple yet.

iPhone 6 Release: A Great Deal Of Focus On Displays

A flexible display means nothing unless the screen itself looks good. Apple was apparently dissatisfied with the in-cell processes used to create the iPhone 5 display, and the company is reportedly contemplating a switch to "Touch On Display" panels, which are currently in development at Apple's Taiwan-based supplier, Innolux Corp. (TPE:3481). Innolux licensed Sharp's proprietary IGZO display technology, so it's possible both technologies could be released inside the iPhone 6 later this year.

IGZO displays, as noted by Tom's Hardware, are extremely thin, power- efficient, and strong enough to handle 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; comparatively, the new iPad 4 can only achieve 264 ppi.

Apple reportedly invested a great deal of time and capital into Sharp's ultra-thin IGZO displays. In late December, Asymco analyst Horace Dediu and DigiTimes both pointed to Apple's quiet $2.3 billion investment in Sharp, believing the cash was used to help bail out Sharp, which had been in financial straits in 2012.

iPhone 6 Rumors: What Will It Look Like Upon Release?

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 translucent Bondi blue iMac from 1998, which let users see the innards of their desktop computers.

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

If rumors prove true, the iPhone 6 wouldn't have to be released with a lot new features to be a best-selling device. Between the iPhone 5 and the security-laden iPhone 5S -- which may introduce NFC technology for the first time, allowing consumers to complete secure mobile payments remotely -- the new phone's possible flexible display is enough to make the iPhone 6 seems like it will be a noteworthy product release for Apple, especially as the company pursues inroads in China, India and other developing countries.

Of the two largest developing markets, China is by far Apple's biggest at market in the world 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.

If Apple can strike a deal, the iPhone 5S and iPhone 6 could also be released on China's most popular network.

Apple wants to get a deal done as soon as possible, according to recent reports.

CEO Tim Cook visited China Mobile headquarters on Jan. 10 to meet with the company's chairman Xi Guohua to discuss “matters of cooperation.” But the pressure is on Apple to seal a deal in Asia: The Samsung Galaxy S4 will be released on TD-LTE this year, which presents an enormous opportunity for Samsung, especially if it can do so unopposed.

Apple will announce its second-quarter earnings after the close of trading on April 23; in its first fiscal quarter ended Dec. 29, the company sold 47.8 million iPhone units.

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