As I said earlier I really don't think Microsoft will try to compete in the tablet hardware arena. Why should they? They can simply put out a good tablet OS and let nature take its course. With a good OS for tablets, the hardware giants will finally be able to compete.
Even Steve Wozniak says he likes the Windows phone OS better than iOS and Android. I think there are a lot of us who are really interested in a tablet OS that is somewhere between the too simple and way too closed iOS and the open but overly complex and way too inefficient and flaky Android. And the idea of running essentially the same powerful and graceful OS on a desktop, a laptop, and a tablet is very appealing to many. And on top of that it will be great to use most of the same peripheral devices on all three without having to rely on kluge third-party adapters.