I think many here are in the same boat, so to speak. XNA was great and I had a lot of fun, now I'm moving on as Microsoft is keeping too silent about it, and excluding it in the ways you already noticed.
There's a workaround to develop XNA projects with Visual Studio 2012 and they should still run on Windows 8 desktop, but there's no official support from Microsoft.
Look at other frameworks/wrappers for .NET/C# like SlimDX if you want to continue this route.
Microsoft seems to want to focus on native code now, it almost feels like a revival movement from within the company, with C++ and DirectX being the combo of choice, even on their Windows Phone 8 platform.
Me myself am completely refocusing on
- using existing game engine for serious game development projects, like UDK and Unity