Apple is expected to unveil the next generation of the company's wildly popular iPhone during an announcement Wednesday.

As usual, the rumour mill has been grinding out a steady stream of speculation as to the upcoming iPhone's features. And unlike past Apple product announcements, all of which have seen feverish speculation in online forums and tech blogs, this one has been preceded by an unprecedented number of purported leaks.

So, as Apple fans count down to the big announcement, here's a round up of the rumours making the rounds online:

NEW iPhone:

First of all, there's no specific confirmation from Apple that it plans to unveil a new iPhone at the media event planned for 10 a.m. PT at the Yerba Buena Center in San Francisco Wednesday. In typical fashion, the Cupertino-based company has issued a cryptic invitation that merely hints at the debut.

“It’s almost here,†the invitation says, depicting an Apple iOs calendar-style number 12.

PRODUCT NAME:

Based on the image sent out in Apple's official invitation to the Sept. 12 event -- which clearly shows that No. 12 casting a shadow in the shape of a number 5 -- there's near consensus that the next-generation Apple smartphone will be dubbed the iPhone 5.

Doubters point to the fact this will technically be the 6th-generation iPhone, however, as well as Apple's abandoning the numbered naming scheme with the introduction of its latest iPad.

SCREEN SIZE:

One of the most persistent rumours has focused on the size of the iPhone's screen, anticipating an increase from the current 3.5-inch display to a larger 4-inche screen, measured diagonally.

Leaked photos from parts suppliers have been circulating online since the summer, showing a version of the iPhone's familiar form stretched to accomodate a screen closer to what Apple's smartphone competition is selling already.

FORM FACTOR:

Other purported parts photos posted online have shown a new two-toned back plate that replaces the last model's glass back with metal. Combined with a rumoured switch in touchscreen tech from on-cell to the slightly sleeker in-cell, the new iPhone is expected to be touted as slimmer than its predecesor. The may only be a millimeter different, but that would be enough for some bragging rights.

It may not be a make-or-break feature, but there's also anticipation the headphone jack will be moved from the top of the phone to the bottom.

DOCK CONNECTOR:

Other leaked photos of the next-generation iPhone point to the introduction of a new, smaller port for connecting the device to a charging cable and other accessories.

Fans have debated the merits of various rumoured replacements -- will it be a 19-pin connector or a nine-pin? -- but either way they're preparing to shell out for a new set of accessories, or the adapter to make the old ones work.

Regardless of the final form, there's widespread acceptance that Apple will continue with its tradition of proprietary parts rather than adopting a micro-USB or other standardized plug common to other manufacturers' gadgets.

Investors can take heart, as rumours point to Apple being the only company that will be selling officially authorized adapters.

SPEED BUMPS:

One rumour that had been circulating ahead of the debut of Apple's previous generation iPhones, and has shown no sign of going away since, is the introduction of the mobile high-speed wireless data technology comonly known as 4G LTE.

Based on competitive pressure, and the introduction of 4G LTE connectivity in certain of its latest iPad models, Apple is expected to bring the iPhone up to speed too.

Reports suggest the next iPhone will be faster, thanks to an increase in its on-board memory, if not a new processor. Forums have been filled with speculation Apple would include a new A6 processor, but many expect the new phone will use the A5X processor introduced in the third-generation iPad instead.

BATTERY LIFE:

In the past, Apple has been known to eschew the latest tech in favour of ensuring its products' users can be assured of a workable battery life. In that light, the power-hogging 4G LTE design is only expected if a rumoured higher-capacity battery is included too.

OPERATING SYSTEM:

Apple's upgraded mobile device operating system, which has been in developers' hands for some time now, is also expected to gets its official unveiling. Expected to be released as a free download, the new iOS will give iPhone users who aren't ready to upgrade their hardware the chance to get in on some of the product launch excitement.

It is expected to be compatible with the iPhone 3GS, iPhone 4, iPhone 4S, 4th-generation iPod touch and the two latest versions of the iPad. Not all features -- expected to include increased Facebook integration, iCloud connectivity, and a new Apple-deisgned map application -- will be usable on all older devices.

RELEASE DATE:

Last year, the new iPhone was released in the U.S. on the second Friday after its public unveiling. If the pattern holds this year, that would mean consumers might be able to get their hands on one as soon as Sept. 21.

That date has received a boost based on reports employees at companies expected to sell the new iPhone have been told not to book vacations during a period that begins that day.

No word on whether the gadget will be going on sale in Canada at the same time.

ONE MORE THING:

The late Steve Jobs was famous for surprising audiences at Apple product launches with a late announcement of something unexpected. If you believe the rumours, Apple CEO Tim Cook might have some options to follow in his predecessors’ footsteps. Will it be a revamped lineup of iPods, a shrunken tablet to fill the niche between the iPhone and iPad currently targeted by products from Samsung and Amazon, or even a refreshed set-top Apple TV box or an entirely new Apple television set? You’ll have to tune in to find out.