Have you ever actually worked professionally with Microsoft tech for any length of time? Have you followed Microsoft closely for 3 decades because your paycheck rides on knowing what's going on with them? If not, I'll forgive you for being an outsider...and yes, I meant Classic.

Microsoft has historically employed over 30,000 developers. That's a lot of people working on new software products. The "churn" you're talking about is, in fact, just more choices for you. It's crazy though you know - you don't have to use the latest thing from Microsoft! (We don't worship them like a lot of Apple-centric devs seem to do with Apple.) Sure, they're trying new things like WinRT and they'd like devs to use them. If things don't take off, they scrap them.

Who cares? You can still use a kit from 1998 (VB6) to make apps on Windows today without too much difficulty. Could you even use XCode from 2005 to make an app for OS X Mavericks? I doubt it.

According to your logic - web developers would never get anywhere because there's so much new tech/frameworks/etc being thrown at them and no corporation to tell them exactly what to choose.