I don't think Microsoft's churn is like that at all. Instead it seems to reflect churn in their internal strategy. They attempt transitions, but abandon them before they are complete. There's no overall trajectory.
The latest is WinRT. Take a look at https://dev.windows.com/ . It's all about Windows 8, Windows Runtime apps, etc. Other technologies are buried. Wouldn't you agree that MS is positioning WinRT as the new preferred way to write for Windows? (If not, their messaging is terrible.)
Characterizing these development options as MS giving developers "choices" is crap. WPF developers aren't excited about having WinRT as another choice, they're worried that WPF is abandoned and their investment is obsolete. They saw it happen to Silverlight. See http://pragmateek.com/is-wpf-dead-the-present-and-future-of-... for example. See http://channel9.msdn.com/Events/Build/2014/2-563 too.
This isn't 1998 and I'm not looking for some Mac vs PC flamewar. These are serious problems. They're making existing developers sweat, and new developers are taking a wait-and-see approach. It's hard to watch, but I'm optimistic about Nadella turning it around.
Oh, and Carbon is not an emulation layer at all, nor is it "heavy handed." Perhaps you have it confused with the Classic environment?