We've heard all this before. Was it WP6? I really don't care enough to remember.
Like Linux, it would be perfectly possible for them to come up with a Kernel that can run on anything from a writswatch to a supercomputer. But they won't.
Like Linux they could then install different types of user experience on top of that, for different types of Appliance. But they won't.
They won't because they can't break the legacy link, unless they are going to give us all a free XP VM to run legacy programmes.