If merger fell through I don't believe ABK would put COD on GP or xcloud and I don't see that changing in the short to middle term.Having a Series/5 only COD on Gamepass would also put it on Xcloud. That could make the potential market larger for Xbox than it would be for Playstation. Of course, this would also mean that they would have to offer it for sale on Xcloud in order to make money on it, and to my knowledge that hasn't happened yet. No game is available to purchase and play as streaming without a Gamepass sub to unless I missed something. The closest thing there is is the Fortnite streaming deal, which is a free game available to stream without a sub.
Wouldn't make financial sense for MS to pay what it would cost to change their minds either.
They have no intrest in it for few reasons, but if they merge all that changes.