UPDATE: Steve Jobs has taken to the stage to tell the world what the new iOS 4.0 firmware is all about - so we've published our full and detailed round-up of the iOS 4.0 firmware.

Apple is set to announce the next version of its iPhone software - cunningly named iOS 4.0 - so we've had a dig around to find out what's likely to appear, and what this means for the next iPhone.

The questions have already started around this release – what will it be? What functionality will it bring? Why would Apple release this now, rather than the traditional March slot?

Well, we've dug around for some answers – here's what we know so far:

Multi-tasking

The iPhone has had a few foibles up until now, and those aren't ever likely to all be fixed. One issue we need to see fixed is the ability to actually do more than one thing at a time on the device, and the good news is that seems likely to happen.

However, we doubt it will be 'proper' multi-tasking the way EVERY OTHER smartphone does – BGR sources state it will be '"A few new ways" to run applications in the background'.

After the backdoor addition of push email in the last OS update, expect this to be much of the same, although there is some hope of a nice UI at least.

The new iOS 4.0 software uses an Expose-like interface, so tapping the home button twice will open up a view of all the running icons, allowing switching or shutting down with ease.

It should be noted that hitting the home button twice on the HTC Desire and Legend brings up the 'Leap View' which is a lot like Expose, although this is for home screens rather than running apps.

Global mailbox and contact icons

One thing that a number of other smartphones have managed but Apple has been coy to add (sound familiar?) is the unified inbox – seeing all your accounts and emails in one place.

Good for those that want to group work and personal emails together, it basically allows a much easier way to organise your messages, according to Apple Insider.

Presumably this will come with an overhauled UI too, as well as folder options, else it could turn into a real mess of messages.

Another minor addition is something we never thought we'd say – Apple could nab an idea from Nokia.

You'll be able to set an icon with a photo of a person on the app home screen, and be able to jump right to that contact's information and ways of getting in touch.

Free turn-by-turn navigation

We're a little more sceptical about this one, but basically Apple has been beavering away at the mapping game, as demonstrated by its purchase of PlaceBase last year.

First Google announced free GPS navigation on its Android handsets (in the US only – grr) and Nokia then followed it up by freeing up Ovi Maps.

Apple tweaked its GPS settings last year to allow turn-by-turn navigation, and although it would be very early, moving onto its own mapping system would allow it to shed the reliance on Google for such things.

Add to that the fact Apple advertised for an engineer to come in and overhaul the iPhone Maps app last year, according to PC World, it makes sense that this will be happening – but whether that will be in iOS 4.0 or something later, we don't know.