As of now even with Activision, Microsoft is not even close to monopolization so not sure why there is even talk about it.
Tencent and Sony are still on top (revenue wise).
While it will most likely change for Sony this generation, Tencent is way ahead.
Also to the OP, Sony by themselves will not be able to compete at some point, that's for sure. But I expect one of the big one to buy Sony (Apple or Amazon).
This would be the best outcome.
A merger with EA or another big publisher can also be good. But Sony cannot acquire them, it is just physical at this point :)
What Microsoft just payed for Activision, is half of the whole market cap of Sony.. I mean :)