The top rumour has to be whether Apple’s September 12 (5am Thursday September 13 NZT) event in San Francisco is for a new iPhone at all (the company is also thought to have a 7-inch iPad in the works).

As usual, Apple has yet to comment, but the timing seems right.

And the last new iPhone, the 4S, was an incremental, lookalike upgrade to the iPhone 4. The odds are that Apple will unveil a whole model on Thursday (one rumour holds it will simply be called "the new iPhone").

We'll take it as read that processor and camera specs will be nudged upward. Here's what else could be on the table:

1. A bigger display. The Wall Street Journal says the new iPhone will have a 3.9 or 4-inch display (the current models have 3.5-inch screens. (smart displays are always measured in Imperial, on the diagonal).

A 3.9 or 4-inch screen seems a good compromise. It would let Apple close the gap on the big screen Androids, such as Samsung’s 4.8-inch Galaxy 3, without the battery life issue getting out of hand, or people losing the ability to wrangle the phone with one hand.

Most pundits think you can take it to the bank iPhone 5 will have a larger screen. But noone’s sure of the resolution, or if it will have a 16:9 widescreen ratio (common to Android smartphones and tables, but so far avoided by Apple in those areas).

2. Slimmer. The new model is said to be thinner. It seems likely, but don’t look for Apple to go overboard in this direction. Remember, the new iPad is actually slightly thicker and heavier than its predecessor. Sensibly, Apple refused to compromise battery life.

Other design rumours include a metal backplate, new earbuds (well overdue), the earbud connector being moved to the bottom of the phone (hope not) and even a new red option alongside the traditional black and white.

3. A new connector. Rumours run from a smaller dock connector to a magnetic one (as used with MacBooks). Let’s hope not. There will be blood on the streets if iPhone, iPad and iPod Touch owners discover their common chargers, keyboard docks, speakers and other accessories won’t connect to the new iPhone. An alternative but unlikely scenario: iPhone moves to the microUSB chargers now standard on most smartphones.

4. An NFC chip. Some mobile commerce advocates say the new iPhone will include support for Near Field Communication, a technology used in many wireless payment systems. But they said that about the last model, too. With few retailers supporting NFC, it’ll be a question of whether Apple wants to move ahead of the market. The answer is usually no.

Do look for Passport, an onscreen voucher system, to be expanded with iOS 6 (iOS is the software that runs iPhone, iPad and iPod Touch; it will also get upgraded with the new IPhone - but the software upgrade should also be available free for older models). Passport supports the likes of airliine tickets and discount vouchers through onscreen codes - but don't hold your breath for wide, or any, support for this feature in NZ.

ABOVE: Photos have been leaked to the internet showing a thinner iPhone. But between Photoshop and Apple's habit of trialing a variety prototypes with different contract manufacturers, the parade of pictures has become near meaningliess.

5. Dual Carrier HSPA+ I know Vodafone NZ wants to see this technology in the new iPhone, and seemed quietly confident when NBR visited recently. So far there are few devices with DC HSPA+ (only supported by Vodafone’s network locally): a high-end Vodafone data stick and the new iPad.

DC HSPA+ supports a theoretical maximum download speed of up to 42Mbit/s (in practice often half that or less, but still not too shabby), twice that of rival networks.

On a related note, the US media has speculated that the new iPhone will support Long Term Evolution or LTE (the new iPad supports both DC HSPA+ - which US carrier AT&T markets as “4G” and LTE).  There’s no 4G in NZ, so for us this one’s purely academic.

Fingerprint security is another hot tip, following Apple's tabled acquisition of AuthenTec $US365 million - but company won't vote on the deal until October 7, after the new iPhone comes out. Maybe something for iPhone 6.

On the software side, look for Apple to ramp up its inhouse mapping solution, Apple Maps, as it looks to wean itself, and iPhone users away from Google Maps. The question though, will be how much, if at all, any new services are available outside the US.

One noteable change, already flagged, is that the next version of Apple's iOS (the software that runs iPhone, iPad and iPod Touch) will drop its native YouTube app - but Google will place a YouTube app in the iTunes appstore from 7pm tonight (Tuesday). A Google insider told NBR the YouTube app will offer better social sharing, and easier subscription and search features fear finger swipe commands, among other frills [see an update here].

Lastly take all rumours with a grain of salt.

Remember that before the launch of what turned out to be the iPhone 4S, noone predicted Siri and, well, let's just forget about the tear-drop design.