Its a good thing for few and bad thing for some, also it wont be a good or bad for most.
For those who see it as Good
-Microsoft - they would get access/ownership to a ton of IPs and games, for their main goal being Xbox Game Pass, it would make the service look more attractive and give them the advantage over competitors.
-Xbox fans - the typical console warring fan would be happy that their favorite company won
-Activision Blizzard - a new form of management would be good especially with who ABK currently has right now, leadership changes can and will occur, the way internal affairs will run could possibly change but you probably wont be able to see the results of that for a while.
For those who see it as Bad
-Sony - the fact that they would have to negotiate with a major competitor is something that they frown upon to get access to IPs such as Call of Duty. It also puts them at disadvantage even if CoD releases on Playstation due to the fact that if CoD gets day 1 release on Game Pass, its gonna be hard to sell a $70 game over paying for a service that lets you play CoD along with other games for far less and on both Xbox and PC.
-Playstation fans - the opposite of Xbox fans mentioned above
For those who are neutral or not affected by this as much (or can go either way depending on the situation)
-Nintendo - getting a Call of Duty game (s) via the negotiation deal that MS made earlier would allow them to finally get Call of Duty again.
-Valve - like Nintendo (although in a lesser way) since Call of Duty just recently started popping up again on Steam. Though the chances of a potential Diablo/Starcraft/etc releasing on Steam is higher now if the deal goes through. However its still 50/50 because like Minecraft, there's a chance we might not still see any Diablo or Starcraft game coming to Steam.
-Gamers who dont care which system a game comes out on - likely wont be affected because if its a game they want, they'll get the platform (or already have it) or they wont get the game at all if there's no interest in it to begin with.
As for me personally - I dont really care if the deal goes through or not - I have access to all the platforms whether its Playstation, Nintendo, Xbox, PC or mobile.
I dont subscribe to any game subs like NSO, Playstation Plus or GamePass/Xbox Gold - so its whatever for me.
Edit: As for Call of Duty is concerned - most of my CoD library is on Steam, the only Call of Duty game I dont have on Steam (that I havent bought already) is Call of Duty 3 and thats console exclusive - which I already have for Xbox.