Again, the vast majority of core gaming users now own a gaming PC, moved over thanks to streaming becoming popular and helping push the format to a level of popularity its never had. There are reports indicating something like 60-70% of users have a gaming PC or laptop now, and I don't see that number stopping its growth.
MS themselves have been seeking this very userbase, first by pushing on Win10, followed by Steam, and thus de-valuing the HW selling power of their lineup. Sony's userbase has been a far more global/casual userbase, and there is simply nothing indicating those users aren't continuing their buying trends.
MS has gone to great length to completely upend their business model from being a HW-sales led one to a service/SW publishing one. It actually fits in with the rest of how the company pushes their SW & services. They have no walled gardens and aren't in the business of it; Xbox is the absolute last bastion of this approach and even that is transforming.
But lets say all of Zenimax/BGS becomes perm exclusives on console on Xbox going forward - is that going to solve their sales issues in the rest of the world, which is really where they have fallen behind to Sony & Nintendo? Highly unlikely. What Zenimax publishes caters to a very US/UK centric userbase and that was already their biggest sales regions. And the games will still be available on another platform, PC, which is at the height of its popularity right now, and whose growth is unlikely going to stop.
I know it circles back to the question of "Why did they do the buy if you aren't gonna make the titles exclusive?", and the answer is still very simple - BGS' output just on its own will still act as a perpetual growth driver for two of their core services they want to expand going forward - GP & xCloud. Getting that many more games exclusives to these two services, in addition to their already increased output, means that each new release has a chance to convert a user into the MS ecosystem via subscription, and if they decide not to sub, MS still gets a premium margin from an individual sale that they wouldn't have gotten otherwise on Steam/PS/Switch. Its a literal win-win. And should some day any platform holder reverse course and decide they are okay with allowing MS' services on the platform, they'll already have audience engagement with several of their IP versus having to appeal to them all on their own with their lineup; it's easier to get a Nintendo-only user to sub to GP with TES6, thanks to the Skyrim ports, if Nintendo were to ever allow GP on there than it would be do it with just Halo or Forza.
