And what is Microsoft going to do with this purchase? Seriously, Microsoft is buy all these game studios and fail to utilize them probably. They own all the IP required to do a followup to Fallout New Vegas and NOTHING.
Microsoft will likely just let them keep operating as they do now, providing money and reaping any profits. They'll only step in directly if the studios are having problems they can't handle themselves, or performing very poorly. They want the profit, not as much to direct everything on a micro-level. EDIT: They will of course make more titles Windows/XBox exclusive too, which makes sense considering the investment.
Yeah, it's not like Microsoft ever bought a game studio that was making a highly-anticipated game, then made them release it as an XBox / PC Exclusive or anything.
https://en.wikipedia.org/wiki/Halo_(franchise)
https://www.halopedia.org/Halo:_Combat_Evolved_for_Macintosh