Possibly. Linus is in a unique position in the world. He gets paid to develop his hobby--which he created and he, essentially, owns. If he's "forced out" from wherever he works, he'll just take the kernel development to another place. If they try to force him out of the kernel altogether, he's quite capable of shutting down the entire product--and no one could fork it off without his approval, as he controls the basic code.
It would be the end of the world's most popular OS. Not sure anyone with any influence would allow that.
I'd have to disagree with you here. Linus can't prevent forks because of the nature of the GPL. There are already kernel forks out there. Some are actually fairly popular, as they are branches for developing/proving new ideas that aren't ready for prime time. IIRC, Alan Cox's kernel is used for this purpose. There have been several ideas that have been more fully developed elsewhere because Linus didn't see them as 'good' until they'd been more fully developed elswhere, which were then later merged back into the main tree.
On the other hand, Linus is in a rather uniq position as 'benevolent dictator' of the main Linux branch. Though not always liked, he's generally respected, which is that allows him to operate as he does. Without Linus, it would be much harder to find someone who could get the same kind of respect and cooperation. In that way, he's pretty much irreplacable at the moment. Who could be the new Linus? I really don't know of anyone who could herd cats as effectively as he can just by virtue of his position.