There seems to be a common misconception here that somehow Microsoft needs to make $7.5b back. They simply don't need to. They exchanged $7.5b of cash for what they value is $7.5b worth of assets.
Getting money back on this kind of deals is done either by selling back the assets or in the long (sometime extreme long) run. 15, 20, 30+ years it does not matter as long as the assets maintains or increase in value.
So no they are not forced to go the 3rd party route and put their game on PS5 to make their money back, they are not forced to increased Gamepass subcription cost to make their money back. They already have their money back in the forms of assets.
The only thing Microsoft should be doing at this time is to make sure that the revenues of subsequent projects exceed the expenses, regardless of the $ 7.5 billion investment.