Metro and winRT are artifacts for tablets and possibly smartphones, including the "bias" to c++. Development for corporate and business in general will be in .NET,WPF, Silverlight and the like for some years to come. You can program for Win8 tablets with .NET if you want, but they want the apps performing for the ARM processors, and they concocted a "runtime" closer to the iron. Microsoft knows the next battle will be on tablets and similar devices, and it will be a fight to the death,
so they have made almost a company bid on win8 and metro. But that does not apply to the desktop necessarily. And the desktop will stay for a long time.
Android and iOS have not seen real competition because they target different people. Let's see what happens with win8, that will target everybody and possibly every platform. Don't underestimate them.