unlikely. EA/Activision are most likely to buy them. Epic makes a lot of money off of the unreal engine, so id MS bought them then they would lose a lot of potential money because they wouldn't want the engine to run on other systems and and developers would have to license a two different engines if they wanted to be multiplatformer or go with another engine. Epic will still have a strong relationship with Microsoft, just look at Valve; MS gave Left 4 Dead 2 a codename even when EA was the publisher.