I'm curious on how a MS merger would be good? At the start, they would almost certainly try to merge user accounts into MSN accounts. Likely force a migration down the line, after merging doesn't work.
The way I think others are thinking about it is that to Activision, making innovative new franchises or long term investments in general is a big risk since they are 100% a games company. Whereas if Microsoft owns them may face less pressure to cut costs/long term investments since it would make up a much smaller part of Microsoft's financials.
Whether that is how things usually turn out in practice with these sorts of acquisitions is a question I don't have a good answer to.
Certainly many would be ok with it. The ones it will hurt will be the heavy users that have multiple accounts, is my guess. Also is annoying to families. Game accounts are just game accounts, even if that has grown. Giving the kids an MSN account did not sit well with me.
I and many other people had their accounts completely borked by the required migration. My lifetime license, gone, either through malice or incompetence. For trillion dollar companies, I always have to assume malice.
Whether that is how things usually turn out in practice with these sorts of acquisitions is a question I don't have a good answer to.