So pretty much your only worried about this deal because of PlayStation. Well Sony didnt care about Nintendo or Sega when they entered the console market and Ms has said they will use CoD like Minecraft. No harm in that. Sony would never allow such a thing when they where trying to wipe out Nintendo in the past. This deal is good for workers, its good for the staff that work at actiblizzard only person who this deal is not good for is Sony as its going to give them competition something they hate as they are used to being the "Rich" Company in the video game market.
I'm worried about competition. Nintendo is still here, and just for the record, I think losing Sega as a competitor in the console hardware market was a loss. I also don't see Microsoft as a trustworthy company (not that Microsoft is alone in this, mind you), and I trust that given the chance, Microsoft will eventually abuse this in some manner that's bad for gamers. And just for the record, I've grown to dislike Sony quite a bit, and if anything, I welcome strong competition against Sony, but this Activision Blizzard deal is quite big for my taste - not that I'm a fan of other acquisitions either, mind you, if they hurt the competition.