I doubt Microsoft will "die" in the sense of going bankrupt and ceasing to exist as a company. However, it seems clear that Microsoft is already "dead" in the Paul Graham sense:

http://www.paulgraham.com/cliffsnotes.html

Similarly, MySpace is already dead in that sense, though like IBM it seems to have carved out a niche as a useful home page / event listing / music player for small and independent bands.