This is frankly unlikely to happen (Bill's comments) for at least two reasons. Firstly, who in their right mind is going to willingly increase their exposure to mobile phone radiation, of which the experts are still unsure how much damage is being done to us. Secondly, Windows Mobile has a really bad reputation in the mobile market and quite rightly so - I have yet to find a user who is pleased with their microsoft powered smartphone. I remember a recent test in one of the UK PC mags where the user needed to make a really urgent call on the Windows Mobile he was testing and it crashed then kept saying something like 'unable to find application phone' (sound familiure - I'm suprised it doesn't bsod!) so I really don't think an MP3 enabled mobile is going to tread on iPod and its rivals any time soon. Hell my P900 has been able to do just that for over a year now yet I have never once listened to music on it. Nor do I intend to.
Don't bin the iPod yet!