The way I view thing is, MS did a lot for gaming, especially when it comes to online MP, but they've overstayed their welcome. They have nothing to offer, and all they're doing is bringing in more bad stuff (timed DLC, moneyhats, paid MP etc all that started with them).
A Nintendo/Sony only gaming world would be awesome, maybe with a third competitor in the mix. MS can just go software only, make Halo, Gears, Forza, etc. for PS/PC.