The Apple iPod is the most successful gadget in the history of the universe. More popular than the Sony Walkman and better selling than the Nokia 3210, the iPod has seen more discussions than DAB digital radio.

But what comes next? How can Apple move forward with new technologies and keep its iPod range a step ahead of the pack? What will next year's iPod range look like?

Future iPods

How about a super-slim 160GB iPod touch with a hard disk instead of flash memory? And would you bet against Apple releasing a resurrected super-sexy iPod mini sporting multi-touch screen and 16GB flash storage?

Surely the future will see an iPod touch, as thin as the current iPod nano but with similar capacity to that of the iPod Classic. That's the current Holy Grail as far as the iPod goes, but it's at least two generations down the line yet.

New features

What we do know is that as we've already seen with every new generation of iPod, Apple likes to bleed features from the top end models into the lower end ones. The new iPod nano, for instance, now has pretty much all the features of the iPod classic. So it makes sense to assume that this year's will be the last generation of iPods to sport the clickwheel instead of multi-touch.

Next year's nano will probably be a touchscreen device. That being said, a change that drastic to the model will probably require a new name. Might we even see the resurrection of the iPod mini tag?

It would probably be quite easy to make a multi-touch nano without making it thicker than the 6.5mm of the current model. After all, you wouldn't necessarily need to put Wi-Fi in it. The nano has always been a barebones MP3 player; it doesn't need the extra bits that would clearly increase size and weight. It would just need the core music playing touchscreen iPod features. No need for all those additional apps and functions.

Apple innovation

At the core of Apple's success with the iPod is its innovation. Apple has always managed to come up with something different when no-one was expecting it to. It went slightly wrong through the first three generations of iPods, but every year since then, new iPod ranges have set themselves apart from the competition.

So what of the flagship iPod touch? Many people are turned off by its limited 16GB capacity. So what are the odds of Apple cutting the iPod Classic from the range completely, and putting its 80/160GB hard disk inside the iPod touch instead? We think they're pretty high. High capacity hard disks are much cheaper than flash memory, even though Apple has managed to reserve 70 per cent of the flash memory market for itself.

What's more, 160GB would be a lot more handy inside the iPod touch than it is in the iPod classic. Imagine all the movies and TV shows you could store on it. No-one wants to watch loads of video footage on the iPod classic, but the iPod touch, with its big and beautiful screen is another story entirely.

Slimmer, better

The 16GB iPod touch is currently 8mm thick, while the 160GB iPod classic is 13.5mm thick. Would people embrace a 13.5mm thick iPod touch if it meant getting a boatload more capacity? We think they would. And that's why Apple is bound to do it.

A move like that would obviously make the touch a bit heavier too, but that is a price that most iPod users would be willing to make. You'd have the choice between a thin, light flash model and a slightly beefier HDD one. Everybody's happy.

They could even add a digital TV tuner like Sony has with the new Walkmans in Japan?

And how about the iPod shuffle? It surely can't get much smaller or it'd be too small and fiddly. So we can expect a capacity increase in the next one, with maybe a marginally smaller form factor. And how about a full clickwheel and a mini screen? The Creative Zen Stone Plus and the SanDisk Sansa Clip both have higher capacities than the iPod shuffle, are cheaper and have colour screens.

Hundreds of millions of us own one, and hundreds of millions more of us will buy one in the years to come. The tipping point was reached ages ago: iPod is the MP3 player of choice in the 21st century, in exactly the same way that Sony Walkman was on top in the 20th. Apple will no-doubt be trying its hardest to keep it that way.

Tech.co.uk's 2008 iPod predictions:

iPod shuffle, new design - 2/4GB

iPod nano / mini - 8/16GB. Multi-touch, core iPod functionality, no apps.

iPod classic - gone

iPod touch A: 16/32GB flash memory, Bluetooth, digital TV?

iPod touch B: 80/160GB HDD