Research firm Generator claims Apple will ship $4.2 billion in wireless-enabled iPods by 2010.

This would put "second-tier mobile phone makers in the shade," researchers said.

"A lot of people don't realise that Apple's iPod business is already bigger than Sony Ericsson. What's more, Apple is the market leader in a growth market while Sony Ericsson is a second-tier player in a mature industry," observed Andrew Sheehy, research director at Generator.

The researchers say that in response to mobile handset operators and their introduction of music playing mobile phones, Apple may simply add mobile phone features to its music player.

Because of its sales volume, Apple can now negotiate deals with suppliers of miniature cameras, video recorders and wireless modems - items normally used in mobile phones - that compete with the deals mobile handset makers can secure.

"Things change when you're buying in that sort of volume. A lot of people who supply components for use in mobile handsets are licking their chops right now: there's lots of new business up for grabs and we know that people are talking to Apple right now about doing this," Sheehy claimed.

The report predicts that Apple will introduce wireless iPods by reaching a wholesale data agreement with one mobile network operator in each iTunes market - a virtual network deal. Users could also then wirelessly publish their own digital content through iTunes.

"The mobile content side is interesting but you could also offer knock-out voice service with this approach - Apple could offer free WiPod to WiPod calls, using a Skype-like software application. A lot of people in the mobile industry will be worried when this starts happening," warns Sheehy.