Really do not see how this is sustainable. Its all very well saying this will create x more subscriptions when its going to gouge a huge chunk out of launch revenue and in the final analysis is just a value-add to GP.
I'm also not sure how the economics stack up - but I think there's potential for a decent argument for it to make sense for the business.
Firstly that COD will make lots of revenue from microtransactions. That business is unaffected.
Secondly, that most people put most of their time into COD's multiplayer.
So, while people may well buy a month of GP to play the campaign and never touch it again, the bulk of COD's players must be looking at getting at least a few months of play on the multiplayer. If you can get someone who would only play COD on their console to sign up for 6 months of Gamepass (at RRP) then they get more money than they would for just selling the game. At about 4 months you're breaking even.
So the questions are:
How much revenue is lost by current gamepass subscribers not buying the game who would have otherwise?
How many people who'd buy the game purely for the campaign will now just buy a month of Gamepass instead?
And I definitely can't guess at what those numbers might be. But, Activision and Microsoft will have the data on how many people sign up for a month to play one game, how many people play COD's campaign and not the multiplayer, how many people play COD that don't have a gamepass sub, and how many do.
What's intangible is how many people this could tip the scales for to convince people to either subscribe to Gamepass and Xbox, because there are enough reasons to go with it. Perhaps you want to play Starfield, Indy, Avowed and COD. All that for $140 for the year, plus whatever other couple of hundred games Microsoft might offer you isn't a bad deal at all.