Following Modern Warfare's arrival on the service later this week, it looks as though Microsoft is preparing another Call of Duty title for Xbox Game Pass sometime in the near future.
It's been spotted that Call of Duty: Vanguard — the series' 2021 entry by Sledgehammer Games — has just gotten an Xbox for PC version via the Microsoft Store. Prior to this, there was just the console version of Vanguard in terms of an Xbox release, and this sort of move usually happens when the team is preparing a title for Game Pass on the backend.
Having said that, this doesn't necessarily mean that we're looking at an imminent addition here. Sometimes it takes months for this sort of thing to turn into a Game Pass release - and with the current focus for COD being on the Modern Warfare series, we'd expect this to arrive a little further down the road.
In fact, next year's Call of Duty should be coming from Sledgehammer Games if the series' development cycle holds up, so there's every chance that Vanguard will arrive on the service at some point in early 2027 to build excitement around the team's next release. We'll just have to see what plans Microsoft and Activision have with this one.