According to Todd Howard, Bethesda Game Studios didn't want to be the studio that made an Elder Scrolls game, then a Fallout game, then an Elder Scrolls game again. It's probably good for the studio if they can do a sci fi game as sci fi has been on their wish list for a long time (actually, they were interested in sci fi during the last production months of Oblivion, before acquiring the license for Fallout).
I am however worried that they still use the ancient Creation Engine for Starfield.
Creation engine's modular, they can rip out and insert whatever rendering tech they like, while keeping their unique but buggy AI and potato face generator.
Interested to see how this turns out. A spaceship based RPG in the Bethesda mould could be fun to play.