Apple revs its next generation iPhone and iOS 5 mobile operating system this afternoon. The details of Apple's announcement are unknown, but the veil of Apple silence is lifting - quickly. Last week Apple sent out invitations to an October 4 event, tagged “Let’s talk about iPhone.” With the announcement date so tantalizingly close, it’s time to take a look at what we know so far about the next iPhone and iOS 5.

What We Know: iPhone 5

Design: There are two theories over what the next iPhone will look like. Theory one is an all-new design device (iPhone 5), which would feature a tear-shaped design with a metal back and a slimmer body, while theory two (iPhone 4S) is that it would look identical to the iPhone 4, but with bumped-up specs. A survey pointed that the iPhone 5 is the most anticipated of the two by consumers.

Features: Regardless of the design of the next iPhone, there are same sure-fire bets over the specs. It’s expected the A5 dual-core processor currently found on the iPad 2 to make its way to the new iPhone, as well as more RAM and a higher-resolution camera, possibly 8 megapixels.

Availability: October 4 is expected to be only the announcement date of the new iPhone, with Apple Insider tipping that the weekend starting Friday, October 14 is the one you’ll want to put aside for queuing outside your nearest Apple store. If Apple uses the iPad 2 model and releases the phone 10 days after the announcement, then October 14 or 15 could see the new iPhone reach the first consumers. The US, UK, Japan, France and Germany are expected to be the first to get the iPhone 5.

What We Know: iOS 5

Known Features: Developers had a chance to play with a beta version of iOS 5 for a few months now, and Apple showcased the major new features as well. The big changes in iOS 5 include several improvements to Mail and Safari, a notification center similar to Android’s, Twitter integration and iMessage, an instant messaging platform for iOS devices. iCloud, Apple’s cloud storage solution is also integrated in iOS 5, so you can re-download purchased music, apps or books to any of your devices or computer, while the master copy resides with Apple.

Surprise Features: Apple is believed to have kept back from the iOS 5 beta one surprise feature – the integration of voice assisted functions in the iPhone. Anecdotal evidence from the likes of 9 To 5 Mac surfaced over the past few weeks that you will be able to dictate texts and emails your iPhone, as well as have incoming messages read to you by the phone.

Availability: If Apple sticks to previous OS release schedules, then iOS 5 should be available a few days ahead of the next iPhone, in order to avoid Apple’s servers melting down. Apple Insider reports Apple has blacked out employee vacations October 9 through to 12 too, which indicates the possible arrival date of iOS 5 to current iPhone 3GS and 4 owners, as well as iPad owners and the 2009 and 2010 models of iPod touch.