Nope. This is forgetting the very big decision that was made during the acquisition: all Zenimax studios still retain control over their IPs. Phil Spencer, Microsoft gaming's VP and head of Xbox, already made this very clear. MS has publicly stated it agrees with how Bethesda and its sister companies operate, and want them to continue in whatever direction each sees fit. So while people with hatred towards Bethesda (justifiable or otherwise) may feel the Fallout franchise should be ripped from their hands and arbitrarily given to another studio, the current owners of Bethesda do not believe so.
Mayhaps, in a time when Microsoft decides it no longer cares much about profits and wants to experiment, what you are suggesting may happen.
Of course, the more likely scenario is that Bethesda just gets Obsidian to develop a game? Since the company has made itself abundantly clear that it is open to licensing out the series to other companies (Modiphius made two Fallouts within the last five years, which people tend to forget since they're not videogames, and Fantasy Flight made another tabletop. As well as Amazon's Fallout TV show coming soon. And how could I forget the already-existing Bethesda-Obsidian project that is New Vegas). Similarly, with Bethesda drawing so much on the older games to attract attention, I would not be surprised if Sawyer or Fargo were taken on as writers for an upcoming Fallout. Was just talking to another user the other day how Sawyer's good relationship with the community could help with Fallout's image problems of late.
