Well, that's a very popular position taken recently in the media. "the PC is dying... Tablets will replace everything we know... look, the sales are going up, it means it's a zero sum game and PC share will go down to ZERO!".
As you mentioned the future is fragmentation, certainly not a monolithic tablet-only future. There are still too many incentives to keep using PCs for many, many usages.
Also for me this is all very familiar. As a pc gamer for years, maybe a decade! I have been hearing about how pc gaming is dying or dead. All the while playing the best games which are usually not released on consoles with the best graphics and performance + controls and setup that I want.
Yeah, and playing on Full HD since a while, while all the consoles out there rely on crappy upscaling to fake Full HD. It's been a while I did not take my Xbox360 or PS3 out. And I'm far from being convinced by the PS4 and XboxOne even after playing with them in the last week.
As you mentioned the future is fragmentation, certainly not a monolithic tablet-only future. There are still too many incentives to keep using PCs for many, many usages.