With Win8 now out, it's clear that WinRT is a managed runtime, a slightly tweaked .Net CLR. Future C++ development for Windows will now require proprietary managed C++, so talk of "standard-compliant" C++ in future versions of Windows is mostly moot, at least as far as consumer markets go. Win8 will be the start of transition towards Windows being a full .Net stack, taking hardware vendors out of the equation.
The old run-time will continue to serve legacy applications but will likely be delegated into running as virtualized. Since it doesn't appear that Win32 will be getting any of the new facilities, Win32 doesn't look like viable commercial option for the future.
I'd estimate that despite being listed as C++, native code in Metro will be phased out during 8 and 9 since C++/CLI Metro apps can just compile to bytecode instead. To those that might remember the "undocumented API" wars of the 90s, this is Microsoft's perfect execution of that. And unlike 10 years ago, they no longer have a monopoly, so they're free to do as they please with courts not being able to touch them.
While it may not seem like a big deal, this change makes all existing tools and just about all third-party libraries obsolete as far as Win8+ goes. And with release cycles, my guess seems to have been quite accurate. Moore's law and current characteristics of mobile devices imply that during the next 2 versions managed runtime will become sufficient for effectively all but most demanding applications, effectively giving Microsoft better platform exclusivity than what Apple has today.
Outside of legacy support, this leaves Google as the last C++ supporter. But unlike Apple or Microsoft, they don't have their own desktop platform, an IDE, a business API (role of .Net) nor a compiler. Overall, a fairly poor position to be in. And with mobile market finally being completely partitioned and interoperability no longer relevant, it might force Google to push for their own exclusivity by introducing their own technology stack, they just lack anything even resembling a mature alternative.
citations needed, citations needed EVERYWHERE!