It seems to me that the silence over the last few months must have been because they changed direction. I'm guessing the the .NET to WinRT was the hold up and they wanted to see if they could do it before they announced it.
Why on earth would you not say that you can use C# to make Window 8 apps unless you didn't know if it was going to happen? I think there must have been some internal politics that made them initially not decide to care about .NET and then eventually they all saw sense and the Dev team worked hard to push it in the stack. It makes sense since the Windows and Dev teams have never had a coherent strategy before now. I think Sinofsky has done well to bridge this divide and get everyone singing from the same hymn sheet for once. (or at least include the dev team in their plans for once!)
I think its all good right now in terms of me using my existing skills (XAML, c#) except for one thing. The big thing about Silverlight wasn't just .Net in a browser. It was the fact that it has the simplest deployment model around, coupled with a near desktop like experience. What in the new infrastructure offers that flexibility? Can you deploy Appx(?) from a server without a full install on the desktop? Its the consistency and ease of deployment that makes SL a lot more useful right now and for years to come. Even when the Win8 is out next year, can anyone honestly think that any enterprise is gonna upgrade to that immediately? My company is still on win xp! Win 7 is scheduled for next year so I think Win8 won't b for another 3yrs at the earliest (probably 4yrs + for some companies). In practical terms, for LOB apps SL will run on more machines, more consistently than any other solution for at least another 5 yrs. MS are committed to supporting stuff for at least 10yrs after release, so I'm struggling to see how WIn8 will deprecate SL usage. Practically,Win8's stack doesn't solve the problems SL has solved. So it seems we in the enterprise world are back where we were 48hrs ago.
I can see a lot of Enterprise and financial companies really not giving a flying fig about the new stack if its not as easy to deploy as SL. Otherwise they would have just stayed with WPF right? Its like MS are trying to close off windows again with embrace and extend where apps are tied to Windows. But the guys who are all making the coolest software right now (i.e. the Silicon Valley people) aren't trying to get tied into anything. They will continue to make HTML apps and design them for the lowest common denominator (i.e. not ie10 or Metro/WInrRT).
As flashy as it all this Win8 stuff all is, I'm not sure it changes the game at all.