If it took them this long to get Vista out the door, do you think there's a snowballs chance in hell they'll get a radically new OS out in a couple years?
What makes you think Vienna is going to be radically different? I'd wager that "Vienna" is effectively going to be "Vista that works", much like XP was "Windows 2000/NT that works".Not necessarily because it's bigger or cleverer, but because in the interim, companies that aren't Microsoft, will have figured out how to write software that complies to Vistas quirkiness.