i remember the time when win xp was released. for about six months there were alot of applications which would not work with xp, drivers were few and unstable, etc.
give vista about the same six months and slowly you'll see how 75-80% of users will build their DAW on it.
and of course there will be many staying with xp, for a while, as i know people (very few!) who are still using win 2000.

things are changing. i am curious how will windows look and work in ten years time...
and i am waiting to see how real 3D interface will work... (holograms and stuff... with sequencers and softsynths.