Before that’s a cause for alarm, however, many of these remaining 20 were key people in New Vegas’ development, and Obsidian also has Leonard Boyarsky and Tim Cain on board, even though both are on Outer Worlds (2), and Leonard and Tim are the original creators of Fallout.
Josh Sawyer, the director of New Vegas, is still there as well and has said he is open to working on Fallout again.
Microsoft has bought up both Obsidian and Bethesda so it is technically possible for them to make another Fallout game.
But at the same time they already announced Outer Worlds 2, and I’m not even sure the key people are necessarily still around.
Source here, which expands further:
Josh Sawyer, the director of New Vegas, is still there as well and has said he is open to working on Fallout again.