APPLE IS EXPECTED to launch its latest iPhone model at its headquarters in California today, after sending out email invitations for a ‘Let’s Talk iPhone’ event.

The iPhone 4 set records for the fastest-selling portable gaming system, having shifted over 1.5 million units within a day of its release on 24 June 2010. Today’s event could be the first major Apple launch not overseen by former CEO Steve Jobs, who was replaced by Tim Cook when he stepped down earlier this year.

Four years after the first iPhone launched and over a year since the iPhone 4, speculation has been mounting for months about what the latest version will look like and how it will operate.

Although the iPhone 5 is expected to be launched today, 9to5mac says the lack of any evidence of a redesign suggests that Apple is actually going to introduce a revamped iPhone 4 –  a 4S – instead and will hold off on the iPhone 5 for another while. Other sites, such as the Washington Post, say that both the 4S and iPhone 5 will be launched today.

Here’s a round-up of some of the biggest rumours around about the iPhone 5 and its potential features:

• Improved voice control, which Bloomberg surmises may bring the phone “closer to the realm of Star Trek-style speech recognition”, to facilitate a greater range of tasks.
• A faster dual-core chip called the A5, which Apple is using with the iPad 2, and new iOS5 software.
• A bigger screen: up from 3.5 inches to 4 inches.
• Introducing iMessage, which will allow iOS5 users to send messages to each other.
• A new teardrop shape which is slimmer and smoother than the iPhone 4. IPhone cover manufacturers have reportedly begun churning out teardrop-shaped cases, but whether they’ve been tipped off about the new device or not remains to be seen.
• Improved camera resolution – up from 5 megapixels to 8 megapixels for the rear camera.
• A new 64-gigabyte option, as well as the 16- and 32-gigabyte versions already being offered for iPhones.

Today’s Apple event starts at 10am local time (6pm Irish time).

Watch: is this the iPhone 5? Prototype of what phone may look like released >