Even after this deal MS are still a fair way behind Sony on gaming revenue.
Apple, Disney or Meta will acquire Sony or buy PlayStation at some point anyway I'd expect. Only deal challenge is with them being a Japanese company. Part of this move from Microsoft is no doubt pre emptive with that in mind.
They cannot. They have a higher market capitalisation (260B for Disney vs 140B for Sony), but Sony has higher revenues and higher profits, and Disney definitely does not have 200B or so to buy Sony. At best, they could do a 1.5-1 merge in favor of Disney.
On the other hand, Meta, Google, Apple, or Amazon could likely afford to buy Sony (in the case of later, funding it via Amazon shares) but I do not see Sony being interested in that for at least another few years. They totally dominated the last console war (more than double the sales of XBox) and despite that you cannot buy a PS5 cause of chip shortage, they still sold more than XBox console. I think they still have the better first-party games, and I am not sure how much long term these purchases will hurt them. For example, Fallout has gone to crap, and the last ES was in 2011, so Bethesda even going full Microsoft, won't hurt Sony too much. WoW was always a PC game so that won't hurt Sony. Call of Duty sure, but then Sony was never that big in first-person shooters (unlike Microsoft who has Halo and Gears). At the end of the day, despite the Bethesda and Activision Blizzard purchase, Microsoft Gaming will still have a lower revenue than Sony.
Saying that, obviously these purchases are putting Microsoft in a very good position to fight back after their defeat in the previous console. I still think that Sony are gonna win this console generation war, but it is going to be much closer, or probably a draw like with PS3-XBox 360.
It would also be interesting to see if Sony has any move. For example, buying SquareEnix and ensuring that FF, KH, DQ, TR and other games become exclusive. I do not expect a Sony-Nintendo merge, to be fair, totally different things.
Then there is always the possibility of a new player entering the scene (looking at Tencent).