Imaginatively called the "iPhone 5", if the blogs are to be believed, the new model is rumoured to be slightly taller, with a slightly larger screen, a more powerful processor and a metallic back.
The dock connector is also likely to be smaller, with the headphone socket relocated to the base of the phone.
The new handset may also feature an Near Field Communication (NFC) chip for contactless payment, and some form of 4G capability.
"It's almost here," was all the official invite said, above the date, Sept 12, with the shadow of a figure "5" underneath.
The venue is the same Californian theatre that was used for the latest iPad launch in March and the reception is likely to be similar.
Ever since Steve Jobs held the first iPod aloft in his trademark jeans and black top, there has been a certain style to Apple product launches (and indeed other tech companies since).
The executive - in this case chief executive Tim Cook - will inevitably be in an open-necked shirt, likely pacing the stage, to an almost evangelical fervour from the crowd.
Tom Merritt, the California-based host of This Week in Tech , has been there and done that.
He told Sky News: "I got to go to one of these announcements in San Francisco when Steve Jobs was still alive.
"They bring everybody in, it's always a dark room and there's a lot of Apple people usually filling the first few rows - so they're applauding and you really feel like you've been brought into maybe not a cult, but almost a different world.
"That hushed excitement, the dark room with the spotlight up at the front that really focuses your attention and all the people there who are extraordinarily and genuinely enthusiastic about these announcements, that can be infectious, it's hard to resist."
There is no shortage of hype around the new iPhone and there will be inevitable queues outside the shops when they finally go on sale.
But there are also questions about just how revolutionary the latest version of the phone is likely to be.
Luke Westaway, editor of the CRAVE blog at CNET, said: "Last year, if you remember the iPhone 4S, when it launched there was this wave of disappointment because it looked exactly the same as the iPhone 4.
"I think that this will be a bigger step forward, but there still is definitely the risk of that feeling of disappointment that it's not living up to all the hype.
"I'm expecting some significant, but not exactly life-changing, upgrades - things like a bigger screen, more powerful processor - moderate upgrades."
The smartphone landscape looks very different now to that in Steve Jobs' day.
According to the latest quarter's figures from IDC, Samsung now has 32.6% of the global smartphone market to Apple's 16.9%, down from 24.2% for Apple in the previous quarter (Samsung's previous quarter share was 29.1%).
The two tech companies are still slugging it out in various courtrooms around the world in their ongoing patent wars.
But later we will find out what Apple has got in the way of new technology - and whether the hardware justifies the hype.