With its commanding market presence, all Google has to do is gradually roll-out desktop enhancements, and there goes the PC. (The list is quite endless given all the vertical market speciality applications; eg libarary search, geo-mapping, etc are just crude examples of what's coming down the pike.). With Linux handling the back-end server requirements, it's game-set-match.
Larry Ellison said pretty much the same thing fifteen years ago - needless to say, we're all still waiting.