They may not ever deprecate W32 apis (I bet they won't) but they also don't need to support it for new development. Hypothetically if DX13 required using UWP and given they want all xbox games to also work on windows, they I believe are doing this through UWP so devs are going to use it for cross platform games etc... Then you get to a point where you can use w32 but are at a serious disadvantage.