My god, some of you people live in the weirdest little bubble, where you have no idea what is going on in the world.
> The consumer PC market has cratered since the iPad
No it hasn't. Not even close. There are a lot more PCs sold per quarter than iPads, and the rate of PC shipments is still increasing.
> How many people really want a Windows machine at this point?
According to every available stat, a vast majority of people choose Windows over Linux and OSX.
> With Valve's aggressive move into taking PC games off of Windows altogether
Valve's biggest market by far is PC, and will remain so for the immediate future. They have no intention of moving off Windows - just establishing other platforms.
> I'd put money on Windows 9 going Metro only
I will take this bet for any odds you are willing to give. The fact that you are even considering this as a possible outcome shows that you have absolutely no idea what you're talking about.