The new WinRT world is not quite here yet - there will be a point when Win10 is so dominant that support for lower versions can be dropped, but that won't happen anytime soon; not with Win7 being as entrenched as it is.
So, for now, it's still WPF for most practical purposes on the Windows desktop. Indeed, that is even the case for Microsoft software - note how e.g. Visual Studio is still mostly a WPF app.
Should the OSDev stop doing 64 bit support, just because the VS team doesn't want to upgrade their tools?
The Office team is making use of WinRT.
As for Windows 7, it might be the new XP, but this time Microsoft is bullying the move into the new WinRT world, so lets see how long it will be around.
The reluctance to move VS to 64-bit is for a different reason. It's doable, but very costly, because of how much old native code is in that thing even today.
On the other hand, as far as UI frameworks go, VS offers a lot of flexibility - it's already a mashup, with some parts using native Win32 controls directly, some parts using WinForms, some parts using WPF, and some parts using HTML5. Basically, as new and better frameworks appeared, new parts of VS adopted them (and occasionally old parts would, as they got rewritten).
But there are no parts of VS that use WinRT (outside maybe of some stuff that relates to WinRT development). For a very obvious reason - there are too many users still on Win7.
BTW, did you know that VC++ guys still have to support the standard library on XP, because the users demand it? I don't mean old versions of it, but even the most recent releases...
So, for now, it's still WPF for most practical purposes on the Windows desktop. Indeed, that is even the case for Microsoft software - note how e.g. Visual Studio is still mostly a WPF app.