Why is everyone so quick to jump to this conclusion ? The regulatory bodies work doesn't stop after the acquisition is complete. They can break it up later as well.
Zenimax did not have any such requirement from any regulatory so it wasn't the same case, but with this so far it seems like a 10 year parity clause is MS's own offer to further the acquisition dealings along.
Why would they want to jeopardize the acquisition 3, 4, 6, or 8 years later ?
I don't know what the future holds, but I do know, generally, businesses do what's best for business. Whatever MS deems is best for their Xbox goals (long-term) is what they'll do. What that is, is yet to be determined and can only really be determined by them.
That said, there are a few common sense things that seem glaring. Making CoD exclusive, to me, doesn't make a lot of sense. It never did. I think there's more money to be had by allowing everyone to buy it. That said, if it were me, while I'd make it accessible to everyone, Game Pass members would be getting all the treats (first access, first access to DLC, campaigns, exclusive DLC, etc). Maybe that was there plan all along (it seems the obvious way to go with this), but they had to make some changes on the fly, due to regulator concerns, and offer parity to everyone else. They can still perhaps offer "Day 1 on GamePass", while others get a normal release, but I'm not sure.
Apart from that though, people need to remember that it's not just IP MS will own; they'll have all of AKB resources and talented teams. You see, 10 years is a long-time in the gaming world; CoD may not even be as big or relevant 10 yrs from now (or, it could be bigger). No telling what the landscape will look like 10 yrs from now. But, with the resources and talent pool MS will have from this deal, I'm pretty sure they can and will release entirely new IPs...created, directed and managed by the same teams responsible for CoD success, and AKB general success. All they need is one of these new IP to be a huge success, and there's no stipulation that new (currently non-existent) IP have the same parity and multi-platform status. MS will play their hand as they see fit, when that time comes. It if it makes sense to keep things exclusive to Xbox and GamePass, they will do that. If it makes sense to release on all platforms, they will do that. If it makes sense for the business to release on all platforms, with exclusive content and Day-1 releases coming to GP (which to me, is the only obvious choice) they will do that.
In the end, this is not the end. This is what people don't realise; this is just the beginning for MS. They will continue to purchase developers. They may go after one or two more big publishers. They won't stop here. They have long-term plans of making their platform (GamePass, not just Xbox) into the premiere place for gaming, whether on a console, your phone, your TV, your laptop, tablet, browser... They don't care where you play, just that you play on their platform, and in order to play, you have to subscribe. That's all this is about...your money.
It's not and never was about "starving PS", or "taking away from PS". That's short-term thinking. Yes, PS is in their line of fire because PS is their number 1 competitor, but the vision isn't to destroy PS. If PS wasn't number one, it would be someone else. Their vision and goal, is to completely dominate the gaming market, for the sake of profit. They don't need you to stop gaming on Sony's platform, or to stop you from buying a PS. What they need is for PS buyers to ALSO be Xbox buyers or GamePass subscribers. What they need is people who play exclusively on Nintendo, to also be subscribed to GamePass, and playing there.
They could care less about another company's financials. They don't need the other companies to fail. What they need is for the people who play exclusively on other platforms, to also become customers of MS/Xbox. And that is how I know, that while they're offering access to everyone, right now, they will do everything in their power to better their GP offerings to entice people who aren't subscribed, to subscribe and keep renewing their subscriptions.