I'm guessing nothing Major , just small ones like IOI interactive is fine I think? They are making Project Dragon exclusive to Xbox, and they make the Hitman series.
Depends on if someone else forces their hand. If others with deep enough pockets go bidding on stuff that XB wants, they won't have much choice but to outbid or lose that option.
MS can likely buy quite a bit more before they seriously have to worry about lawsuits and the Gov becoming an issue, depending on what they bought.