Since Microsoft's acquisition of Activision Blizzard, there's been lots of speculation about the team's library and how it'll work with Xbox Game Pass / Xbox Cloud Gaming. The details aren't exactly clear right now, but work relating to some of ActiBlizz's biggest series' could be going on behind the scenes.
As posted over on Reddit, 2015's Call of Duty: Black Ops 3 has been spotted on Xbox Cloud Gaming. The Reddit user says that if you try and play the title through Cloud Gaming it doesn't work yet - the game freezes on bootup and returns you to the store page.
At the time of writing, Xbox Cloud Gaming only works with select Xbox Game Pass titles, so this Black Ops 3 appearance perhaps hints that some sort of testing is going on for CoD on Xbox Game Pass / Cloud Gaming. This hasn't been confirmed by Microsoft though — and we've seen other games crop up like this in error — so it's maybe best not to get your hopes up too much for now.
We'll keep an eye out for any more news on this, and indeed, if any other ActiBlizz games start mysteriously cropping up as Cloud Gaming compatible. Remember, Xbox signed lots of Cloud Gaming deals in regards to the ActiBlizz catalogue last year, so exactly how these sorts of games will work on the cloud remains to be seen.