MS would keep the game on PS. That their honored deal. The let PS keep bethesda timed exclusives.
Unless it's timed exclusives, MS can modify it.
They can't modify it without Sony's consent, since Sony is one of the involved parties in the original deal along with ABK. So it would only change if Sony agrees to allow the change.
It will only be issue, if MS doesn't allow it on the console.
Keep in mind, that MS wants gamepass day1. They won't sit down for 3 more years of marketing, considering the marketing deal expired in 2024.
MS could've paid Sony out of the timed exclusivity for Deathloop and Ghostwire. They did not.
They could pay Sony out for marketing rights to COD Modern Warfare 2. Chances are they will not, because it could create unfavorable optics for them in the middle of this deal. ABK would have to prove beyond any doubt that they gave MS co-marketing rights for MW2 strictly on normal terms and not at all influenced by the impending acquisition.
What could (temporally) block MW2 being on GP is a potential marketing deal with Sony if it exists and if it's the same RE Village had. That block would be effective independently if the acquisition is closed in time or not.
If the Sony deal doesn't exist for this game or exist but doesn't has that game subs related part, I assume it could be included in GP independently if acquired on time or not.
It would be crazy if Sony took GamePass into consideration for RE Village but not something significantly bigger like COD, but I guess crazier things have happened.
They can attempt to buy out of it, but Sony will say...
Actually I wouldn't be surprised if Sony accepted that type of offer if the money was right. And if MS are desperate enough for something to "make up for" Starfield & RedFall delays, they would likely be willing to pay a few hundred millions.
But how's that probability looking like? Kinda low.
If MS prepares everything for the ftc, then yes.
I wouldn't rule out the deal closing at or before December but again it's about probability. And the probability of that happening is like 10% at best.
And even if they can, if Sony still has marketing rights for MW2 and beyond for another year or two, MS either has to honor what those are (likely including no Day 1 into GamePass), or pay Sony out of the contract.
In this case though, I think they actually would pay Sony out of the contract, for various reasons. Too big a franchise to not do so, unlike Deathloop or Ghostwire Tokyo.