We're only a few hours away from Apple's big product announcement in San Francisco, where the Cupertino, Calif.-based company is expected to announce its next-gen iPad, called either iPad 3 or iPad HD, and a new Apple TV device. Leading up to the big event, however, Apple has shut down its online store.

We'll be back soon, reads a message on Apple's website. We are busy updating the store for you and will be back shortly.

Underneath the message are contact numbers for each country's Apple telesales team.

Apple is likely refurbishing the site to upload its new products, the iPad HD and the new Apple TV, but the company could also be redesigning aspects of the store as well. With the recent acquisition of Chomp, Apple is expected to announce revamps of its App Store and iTunes Store. There's a good chance that Apple might also want to upgrade its own online store in this way, in order to better parallel its other stores.

If Apple overhauls its iTunes and App Store platforms, it would be the first time those designs have changed in about three years:

The new design is said to be even simpler and more user-friendly than the current design, said Mark Gurman, who originally reported the story on 9 to 5 Mac. Apple is working on ways to enhance the speed and efficiency of finding new content, such as songs, videos, and applications. The cornerstone element of Apple's new iTunes Store is interactivity. As Apple vaguely explained to a number of music labels and entertainment partners, Apple is looking to make the iTunes Store a much more engaging experience.

iPad HD Event: What to Expect

The iPad HD is said to feature an improved camera, a bigger battery, and a dual-LED backlit system to power an 2048 x 1536 true HD display that looks, according to a source who spoke to The New York Times, truly amazing. Apple's dual-LED solution makes the iPad's screen noticeably brighter, but it also apparently solved several puzzling issues with heat dissipation and battery consumption.

The iPad HD will also apparently be the first Apple iOS device to feature the high-speed 4G LTE network. The Wall Street Journal confirms that AT&T and Verizon Wireless are getting ready to sell an LTE-capable iPad, which could achieve faster download and upload speeds compared to 3G technologies, and Reuters again confirmed the news on March 6.

Apple originally hoped to include LTE in the iPhone 4S, but the current implementations of LTE in phones caused very short battery life, which was a major complaint by users. Apple CEO Tim Cook, in a company earnings conference call in April 2011, said first-generation LTE chipsets force a lot of design compromises.

The iPhone 4 PCB [printed circuit board] is already incredibly small, not leaving any room for an extra chip to enable LTE without shrinking the size of the battery, said Anand Shimpi, a chip expert and CEO of Anandtech.

Fortunately, Qualcomm recently unveiled the fifth iteration of its new chip, which supports TD-SCDMA, TD-LTE, HSPA+, EV-DO, embedded GPS, and LTE on TDD and FDD networks worldwide. The chip works withAndroid and Windows 8 devices, but by targeting so many different carriers, there's a high degree of likelihood that this will be the same chip inside the iPhone 5.

Apple has also reportedly upgraded its front and rear cameras for better Facetime and pictures. This is no surprise -- the camera system on the iPad 2 is now considered low-end, given that it only records up to 720p HD and requires tapping to focus. Assuming Apple outfitted the iPad HD to shoot stills and video like the iPhone 4S, expect autofocus, video stabilization and full 1080p HD video recording.

Another reason to believe the iPad HD will shoot 1080p video: Starting late last year, Apple reportedly asked several movie studios to submit content to the iTunes Store in 1080p.

Thus far, 1080p HD content has largely eluded users of Apple products, with HD versions of videos on the company's digital download service maxing out 720p (1280 x 720) and chief executive Steve Jobs balking at adoption of Blu-ray on Macs due to licensing complications and other challenges that he said threatened to translate into a 'bag of hurt.' But that could begin to change later this year, as a handful of feature films being submitted to the iTunes Store for a release in the September and October timeframe are being sent with documentation for an optional 1920 x 1080 resolution, according to people familiar with the matter.

Apple is expected to launch a new version of its operating system, iOS 5.1, along with the iPad HD. If this is true, iOS 5.1 could offer support for 1080p HD videos. If this is the case, the update would also apply to the Apple TV device, which currently maxes out at 720p HD. In this way, users could start watching full HD videos on their new Apple TVs and new iPads starting in early March.