When even one of Metro's former developers doesn't use Windows and Microsoft is making noise about bringing the classic desktop to ARM tablets isn't it clear that Microsoft doesn't really believe in Metro?
That said, I also doubt that Microsoft can bring its old x86 Windows look and applications to ARM in a way that will work. I think the Metro interface will be a total failure on the desktop, but I think that “Classic” Windows on a tablet or a smartphone will be even more of a design flop.
Leaving aside the foolishness of trying to use a Windows, Icons, Menus, and Pointer (WIMP) interface on a tablet, there's the engineering problems behind the display. It's not that easy to port old x86 code and recompile it for ARM.
You could, I suppose use an Apple-style Rosetta x86 binary emulator for ARM, but that approach has three major problems: 1) It's slow; 2) It eats power like an elephant eats peanuts; and 3) you're still stuck with very different screen architectures.
Sure, I can see why the idea of using Desktop on ARM sounds attractive at first glance: “Give the people the interface and apps they already know,” but practically speaking it comes with a host of problems. Not least of these is that it makes me wonder, yet again just how really ready Metro is for any users on any platforms.