> Not only that, like Mac OS X, Windows is moving into another application model WinRT with containers. Just like Carbon, only selected Win32 APIs will survive in the long run.

Microsoft would still let you run 16-bit DOS apps on Windows if Intel hadn't dropped compatibility from their 64-bit processors. Both of us will be dead and buried before Win32 goes away.

Sure, but it doesn't change the fact that one day it will be gone, specially if Windows 10 becomes another 7.

> Which leaves the question how much POSIX can be implemented on top of WinRT.

> Similarly not all POSIX calls are allowed inside Mac OS X App Sandbox.

Except that WinRT as well as OS X Sandboxed App are all unpopular and therefore unlikely to replace the regular apps anywhere near in the future.

If you prefer another set of examples, iOS, Android, Arduino, HTML 5.

For me POSIX is a kind of unofficial C runtime.

Now with systems moving beyond C, POSIX matters much less.