No direct source to link as of making this OP as the podcast this is being confirmed on is still ongoing.
But yeah for a good while now there have been so many rumors that certain Microsoft published first party games would be making the jump to other platforms, leading to a lot of speculation on if Microsoft might be opting to go third party in the near future. Phil Spencer has now officially clarified that the whole "third party" thing is not true and that BIG games like Starfield and Indiana Jones are going to stay Xbox and PC exclusive. However he has confirmed that yes FOUR first party games are going to go multiplatform. All four games in question are titles that have "been out for more than a year," two of them are "smaller projects," and two others are "community driven" titles. As for what the games are, Phil Spencer said he doesn't want to outright say right now as he wants the devs to be the ones to confirm them when they feel comfortable.
Even so I'm gonna speculate anyway.
My guesses on the two "smaller" projects:
- Hi-Fi Rush (dataminers already found new outfits in a recent update that are clearly meant to indicate new platforms for the game like Switch and PlayStation)
-Pentiment (a smaller project from Obsidian, a story driven narrative role playing adventure)
My guess on the two "community driven" titles:
-Sea of Thieves (a live service pirate MMO from Rare that has a decent sized player base, and safe to assume Microsoft is hoping for even greater player numbers by porting it)
-Grounded (another Obsidian game, this time a survival game with co-op that is pretty popular with people who love similar titles like Minecraft)
Those are my guesses at least, and it wouldn't shock me if one or all of them get Switch versions confirmed during a Nintendo Direct (Nintendo almost always has SOME kind of Direct in February).
Also sorta related, they also brought up the subject of "Activision-Blizzard games on GamePass" and at last we know when something will come to the service, namely Diablo 4 is coming to GP in late March, so I would expect other stuff like Call of Duty, Crash Bandicoot, and Spyro won't be far behind.