Yup, Could even add an option in the OS to boot into 'full' windows if they have it too. They could sell the two versions separately, i can't see why microsoft wouldn't, it's like free money for just getting rid of stuff. Obviously the reasoning behind not doing it up until now is keeping the 360 alive, but if they could make so much more money from just making everyone play on PC next generation why not?
They could even port the 'cheevo system over in it's entirety and build it into the OS as opposed to a crap shell over the top like GFWL so 'cheevo whores can keep them. Although online gaming will obviously be free, otherwise i'm pretty sure valve would just make a competing OS and win. Or no PC gamer would bother buying the OS and stick with regular windows, defeating the point and losing a fair number of buyers.
They could even port the 'cheevo system over in it's entirety and build it into the OS as opposed to a crap shell over the top like GFWL so 'cheevo whores can keep them. Although online gaming will obviously be free, otherwise i'm pretty sure valve would just make a competing OS and win. Or no PC gamer would bother buying the OS and stick with regular windows, defeating the point and losing a fair number of buyers.