I have never consider it alive to begin with. I never understand why they even make such eleborate video to begin with.
Speculation from a few comments on Engadget.
MS was hoping to slow iPad sales by releasing more videos and leaking a 'tentative release date'.
I think they were going to release something, but realised that with their partners deserting Windows left, right and centre then they could no longer afford to introduce another OS paradigm.