The issue is that PC gamers are not a majority of the desktop market. Game developers and similar software developers would take interest, sure, but OEMs still likely wouldn't put Linux on their machines (maybe builders like CyberPower, though). I can't really see businesses moving that way, either (not in a 10-year time frame, at least).gamers move to linux, software developers take a bigger intrest.
software takes a bigger interest, oem computers think why put microsoft on it?
oems start using linux as a system line, businesses start looking at it and wonder "why pay 1-300$ a computer for microsoft when everyone uses linux"
businesses use linux, pro software decided to move to it also
and microsoft dies.
I guess I'm just not as optimistic as you, but as much as I don't like Windows 8, I really don't think it's going to fail as catastrophically as people are expecting.this could happen over the coarse of 10 years. i really see this as a possibly if the next windows doesn't return to a desktop friendly layout as a default.