If windows 8 flops then yes they are in trouble. If it’s a hit then no.
Very well and succinctly put.
The tablet market is plenty big enough for many players, if they have products people desire and can use productively. Right now, as someone pointed out a few months ago, there is no "tablet market", there is an "iPad market", consisting of the Apple iPad and a bunch of iPad wannabes. But that will change as the non-Apple tablets figure out what they are.
I doubt that Win8 will overcome Apple's leadership position, but if it does well enough, it will keep the other players alive to compete. And there's nothing wrong with competing successfully while not becoming Number One.