It looks like Microsoft did cut some people at Obsidian. I see Josh Sawyer 8 days ago retweeting (or whatwver the Bluesky term is) various "got laid off, looking for work" messages from some Obsidian people who got cut. I don't think that they were from the Fallout: New Vegas team, though (at least the two mentioned).

https://bsky.app/profile/jesawyer.bsky.social

Jay Turner:

I and a good number of very talented game devs were laid off by Obsidian as part of the Microsoft sacrificial rituals this morning. If you or anyone you know is looking for a Senior Writer/ND with more than two decades' experience in titles like Dragon Age and Mass Effect, please let me know!

https://www.igdb.com/games/fallout-new-vegas/credits

Not on the New Vegas credits.

An area designer "bre_z".

Looking for work</3

Not sure of full name, but looks like "Bree" as a first name? Nothing like that on the New Vegas credits either.

EDIT:

https://www.pcgamer.com/gaming-industry/fallout-co-creator-tim-cain-is-out-of-retirement-and-back-at-obsidian/

Fallout co-creator Tim Cain is out of 'semi-retirement' and back at Obsidian

https://www.pcgamer.com/games/fallout/fallout-co-creator-wants-to-make-one-last-game-before-he-retires-for-the-second-time/

Fallout co-creator wants to make one last game before he retires 'for the second time'

So the original Fallout guy is back too in the last several months...and that's despite the studio laying off 25% of its staff.

https://fallout.fandom.com/wiki/Timothy_Cain

Timothy "Tim" Cain is the original creator of the Fallout series and setting. He was the lead programmer on Fallout and one of the six people responsible for the game's original design.

EDIT2: and they do say, in the article, that at least some Bethesda people will have some level of contribution:

The only Fallout game in the last two decades to not come from Bethesda was 2010’s Fallout: New Vegas, developed by Obsidian and directed by Sawyer. Although New Vegas has become a fan favorite, Bethesda has maintained control over the franchise. The Rockville, Maryland-based studio will work with Obsidian on the new project, the people said.

So that's people from the whole series being brought in on this.