@kettch: That's what they said about WinForms, and then WPF, and now WinRT. Then it will be WinNext, WinNext2, 3, 4, ... until there are so many platforms that Microsoft has lost sight of compatiblity and basically turns into a retailer releasing version after version only two weeks apart. Pretty soon I feel companies are going to get really tired of re-writing their applications.
I think is it clear to everyone that there are too many plaforms, the problem is how to get rid of some of them (at least the most obsolete ones) given the amount of legacy software that cannot be easily rewritten and the need to innovate.
WinRT seems evolutionary enough from WPF that it would probably not be the most difficult part of the evolution. I am more worried about applications using WinForms not going away for a very long time.