It's not just one announcement; they keep changing their mind about what the future of the windows API is. WinRT is the final nail in the coffin. Now with WinRT on one side being tied to Windows Store apps and .net/WPF on the other side being limited to normal desktop applications, who in their right mind would devote time to building an app in either?
In particular, if you're making enterprise software, for example, and aren't interested in the Windows Store, what can you do except throw up your hands in the air and switch to the web.
Even if you're determined to make a desktop app application, at this point WPF seems even more likely to become problematic in the future than the Win32 API!