Microsoft will most likely end up owning Activision Blizzard by next year. While it may be a foregone conclusion, the tech giant will have to work for the purchase. After Saudi Arabia and Brazil gave it a thumbs up, Microsoft is having issues with the Competition and Markets Authority (CMA), UK's regulatory body.
Unlike most others, the CMA has started a second and more in-depth investigation into the buyout, which appears to have offended Microsoft.
Basically, the CMA is afraid that giving Microsoft the ability to put a game like Call of Duty into the Xbox exclusively is bad for the market. On the other hand, Microsoft is doing all it can to reaffirm that it will not pull Activision Blizzard games off PlayStation.
You can't exactly blame the CMA for casting doubt on Microsoft and its long-term plans for Activision Blizzard properties. After all, Microsoft is keeping future ZeniMax Media releases such as the likes of Redfall and Starfield as well as potentially The Elder Scrolls 6 and Fallout 5 on the Xbox Series S/X. It wouldn't be out of character for Microsoft to do the same for Call of Duty, among many others, as soon as the existing agreements in place with Sony have expired.
Sony believes that making Call of Duty exclusive to the Xbox is enough to make fans switch platforms. However, instead of doubling down on its argument that this will not happen, the tech giant claims that Sony will still enjoy a "significantly larger" user base compared to Xbox in a statement shared with GamesIndustry.biz. Furthermore, Microsoft believes that making Call of Duty exclusive would only serve to "alienate" and have a negative effect on the Xbox as well as the Call of Duty brand. But, Microsoft did say that Sony "has the ability to adapt and compete", adding that "gamers will ultimately benefit from this increased competition and choice."
TLDR; Microsoft is just throwing everything it can to the wall to see what sticks.
Ultimately, all we can do is wait for the CMA to share its findings in March. Until then, Call of Duty fans can keep themselves busy with Call of Duty: Modern Warfare 2 and Warzone 2.0, which are coming out on the 28th and November 16, respectively.