Generally speaking, there are two driving forces for a buy-out/purchase:
- desire to cash in on the existing IP
- desire to expand the existing IP for even larger profits

While the former is surely a given the later may or not have any creative vision or energy(s) behind it. There might be cases that a larger company can help a smaller one evolve into a larger market or market share however when the smaller companies products have already mostly reached their potential being part of the larger company might only provide additional overhead, "red tape" or "creative breaks" on what the teams might be working on or produce.

IMHO: the online multiplayer FPS has been done to death already.

Maybe if Microsoft made use of some its Billions of "AI" investment and funneled it into NPC behavior's or procedurally generated gaming environments we might see innovation in the genre.