I think your post is very on point. What we've seen play out in the past 10 years but accelerated recently in the video streaming space was just a precursor to the gaming world that, frankly, we should have all seen coming. Companies value subscription revenue, it's more valuable to their investors for one. You can't garner a critical mass of subscribers to support the platform costs unless you have an arsenal of content to go along with it. That's why Netflix, HBOMax, Disney+, etc. are spending obscene amounts of money to produce content to lure people to their platforms.
Gaming will be no different. Microsoft is clearly heading in the direction where Game Pass is their consumer subscription service that rounds out their commercial subscriptions in Windows/Office. They have the platform and a decent amount of content but this will push them over the top and make for a very compelling offer for what $15/mo gets you. As a long time Xbox owner, I don't personally care whether Sony/Nintendo get these games or not (though I'm sure they do). What actually excites me is Microsoft's stance about including these in Game Pass and generally assuring me that I can play them on PC AND Xbox, hopefully they can bring some more cross-play support between those two platforms as well since third parties have been so inconsistent with it. I expect other studios will continue to be snatched up but I also think others have made good comments in here that none of this precludes great content from arising from other Indie developers. After all, almost every game we celebrate today from the "big players" started off as a small entity that grew. The large studios, to my recollection, haven't been great about starting new content (just look at companies like Amazon that can throw endless money at a project and how many failures they've had).