Sony has exclusives, too. MSFT already said their top Activision-published titles would also be available on PlayStation, such as Call of Duty. Sony also buys studios and forces exclusivity agreements on them, too.
Could this acquisition also put Sony in a tough spot? Sure, but that's the nature of the game they are playing (no pun intended), and don't forget, there are still a ton of incredibly popular third-party titles that are available on PlayStation, such as FIFA, Madden, Fortnite, etc... and won't be exclusive to any console in the foreseeable future.
There's nothing preventing them from making game-changing acquisitions, either. Sony could acquire EA, Nintendo, or a whole bunch of other top game companies and nobody would bat an eye.