Expecting millions to get an Xbox/PC is different from expecting a paradigm shift. Yea millions would probably get an Xbox for COD but I doubt it would be in the amount necessary to sustain COD. Jumping platforms isn’t something that it’s easily done what more for just one game.
The more realistic scenario is that while some would switch for COD the overwhelming majority would stay where they are. I can see like maybe 10 million at most switching, the rest will probably stay where they are and move on to a different shooter or game. It would be far more disastrous to the COD franchise than it would be for Sony to be honest. That’s why I believe MS when they say they have no plans to take COD away from Playstation.