Is that likely to work in XP though? (That is how the Mac OS deals with it, but I gather that is software based.)

The thing about running XP only on the Macs is that there's not going to be an Apple warranty or support that way. This to me seems to limit the idea only to those with the technical knowhow to handle this anyway. The average user isn't going to go for a solution that has no manufacturer support. So I don't really see a huge market for Macs with only XP.

Now dual boot I can see, perhaps, as long as again it doesn't void warranties. Still, so far the bar of entry is still pretty high, a lot of technical work to get it going. What I do expect will happen with commercial developer resources behind it, though, is the ability to run Windows concurrently with Mac OS, a la Virtual PC. That's not really anything new, but Virtual PC has always been a slowish performer. Since this is now Intel hardware, though, it should be possible to have a Virtual PC-like dual use setup with little to no performance hit. That is the solution that will sell to the average user. Those who need no support or warranty will still be able to make XP boot if they want.