Seriously, the suite hasn't even hit the beta release yet. Microsoft has an
internal target, which they aren't sharing, and that's subject to change as
development and testing proceeds. Don't expect to hear anything more than
semi-informed guesses for several months yet.
If the disasters of W2007 are to be avoided and the heaps of serious bugs of
W2007 are to be resolved, my guess is that release before 2010 is most
unlikely.