what's the word ... oh yeah, Never Happening.
seriously though, there's no way ms would try to do this. if for no other reason than there would be no way to stop people from buying the xpod without buying a xbox2. i know a lot of people (myself included) who would love to get an ipod (or the microsoft equivalent) for $100. unless microsoft could come up with a way to only be able to use the xpod if you had an xbox2 (or if they sold it to people who didn't have an xbox2 for a higher price) they'd go broke selling it for $100.
plus, realistically, i think microsoft has learned its lesson at using hardware as a loss leader--it's one thing to lose $10 on each unit sold; it's a completely different beast to lose $100+.