With the deal that closed back in October, means that Activision now falls under Microsoft and this has many awaiting the time when Call of Duty is added to Game Pass, which has been rumored for a while. It has been said before that COD would be coming to Game Pass, but so far no one knows exactly when it would happen if it does.
Recently, a Reddit user had seen one of the COD games listed on the Xbox Cloud Gaming catalog which makes many believe that the game is being prepared to be released as a Game Pass game but nothing is official yet.
It is believed by GameRant that the game becoming available on Xbox Game Pass could help with some issues the game has, or even just make the experience better. One thing that was discussed was the storage of the games, Modern Warfare 3 came to a size of 200GB on consoles when downloaded. The game could be compressed if it is added to Cloud Gaming which would solve those problems completely.
Something else that could happen to benefit the franchise if the game was brought to Xbox Game Pass is, they could do promotions where if a user has Game Pass, they can make in-game purchases for a bit cheaper or just do exclusive content for users every so often. So far nothing is confirmed for sure.
Call of Duty is available for purchase on Xbox Series X/S, PS5, and PC.