I agree with you regarding the Obsidian part, and I more or less said as much in my first post in this thread. Obsidian are eager to make another Fallout game.

The question is, however, whether Bethesda would let them, and if not, why not. And you have not addressed this part adequately.

These are the guys who made some of the best games of their respective years, they don't have the maturity and professionalism of a toddler having a tantrum.

The lawsuit against Interplay suggests otherwise. Interplay had sold the rights to Fallout to Bethesda, with a clause that stated they would be allowed to make a Fallout MMO. When Interplay failed to get enough funding to move forward with the MMO quickly enough, Bethesda sued them to shut it down. Bethesda also tried to claim that Interplay only had the rights to the Fallout name and not any of the other elements from the game, such as super mutants or power armor. This meant that any Interplay Fallout MMO, if it was produced in the end, would not resemble Fallout at all, and would only be Fallout in name. This then led to Interplay hitting back, saying that if Bethesda only intended for Interplay to get the Fallout name, then there was a failure in communicating the rights granted in the original contract, and thus the original contract is invalid. It's a whole big mess that could've been much simpler, but Bethesda decided to make a dick move.

And having gameplay elements in Fallout 4 that appear similar to elements from New Vegas does not show that Bethesda's okay with Obsidian.

You don't think there's bad blood between Bethesda and Obsidian? Fine, that's a valid conclusion. But from where I'm sitting, I don't see two companies who are likely to collaborate again in the foreseeable future. I would love to be proven wrong, I would love to see Obsidian make another Fallout game. But I don't see it happening.