i don't think it's nescesarily a case of mac switching to windows, more of a case of there being 1 operating system for both mac and windows, made by joint venture between the two companies, or maybe even a third party
Macs will run XP on them right now, thanks to the new dual core Intel processors (which, by the eay, run WAY faster on a mac than they ever have on a PC)
i still prefer the mac OS, it's so much simpler, faster and more stable than XP