Well, I believe Phil has already answered how exclusivity will be handled. I believe he said it would be on a per-game basis, so that should tell you that some games may be exclusive and others may be multiplatform. The huge games like Fallout or Elder Scrolls I could see MS keeping multiplatform but then others like Doom, Wolfenstein, and Dishonored, etc... being Xbox/PC only. So I guess.... nobody really knows how MS will handle it, maybe everything will end up being Xbox/PC only or maybe everything stays multi-platform or like I said, maybe a mixture of exclusivity and multi-platform.
My initial thoughts after seeing the acquisition news was that the games would release day one on Gamepass and on the PS5 for $70 as Xbox users gain massive benefits from having all these in Gamepass day one and PS5 users can still pay them a premium to play it and everyone wins and plenty of $$$ is made.
but now after a few days I'm not so sure if that will be the case realising that Elder Scrolls and Fallout are now potentially the two biggest platform sellers that Xbox currently have in their library.
The first option of putting them everywhere will make the most money in the short term for sure but the second option of bringing in more people to the ecosystem either on console or PC via Gamepass subs or profits from the 30% cut from third party game sales will likely be the strongest plan in the long term.