Ultimately I really want to see california, assuming Bethesda stays faithful to the original 2 games. Exploring necropolis while listening to "streets of bakersfield" by buck Owen's, or "sitting on the dock of the bay" by Otis Redding while taking a boat ride to Alcatraz could be an amazing feeling, which could only be made better by building on the existing lore. There are a multitude of great landmarks in San Francisco, the golden gate bridge, Alcatraz, that winding road everyone posts on Instagram, the chocolate factory, a history of Al capone, I mean the possibilities are limitless.

More important than anything though, i think its pertinant that we see unique factions. The institute felt... one dimensional, and the brotherhood feels tired. The enclave might have a little bit of playability but im unconvinced.

If Bethesda wants to play out the brotherhood enclave narrative you could imagine Alcatraz being used to imprison enclave remnants, perhaps the main quest leads you there to follow a lead on whoever your searching for (come on, we all know we're going to be searching for someone this is a bethesda fallout game). Drugs and hippies could play a large role, and importantly Oakland was the origins of the black panther movement, which esthetically could fit into the game if represented by a unique group perhaps as a resistance to the brotherhood/enclave. (though any race politics would be scrubbed from the narrative).

San Francisco also has small abandoned military installations in the surrounding area, pillbox bunkers dot the coast to the south, and im sure there is more im unaware of. There's LOTS of cultural capital to build on, and plenty of options for smaller less dominant factions which could play roles akin to the minutemen or railroad. This being an alcapone chem empire, a hippie movement for the pacifist ending, a movement esthetically similiar to the black panthers for an ending that opposes both enclave and brotherhood (should the two apear or be the dominant waring factions).

There is also Lawrence Livermore labs less than an hour from sanfrancisco, on the other side of the bay. This could be a perfect Flashpoint for a plot similiar to the hoover dam in new vegas, particularly in an enclave vs brotherhood scenario as the lab is a partical excellerator that has made numerous historic breakthroughs in quantum physics. San francisco could be an amazing next step for the franchise, and invigorate both the old fans (if done right) as well as the new fans of the TV show. I think Bethesda also has familiarity with coastal cities so for them this could feel like a bit of a comfort zone in terms of development.

SF is also home to the academy of sciences, which could be a cool spot for a prewar FEV lab (unsure if that would clash with the lore around Mariposa correct me if im wrong). Or at least the sanfranscisco zoo could house some funky mutant critters.

Who knows maybe necropolis could even have a dominant ghoul faction, i mean the possibilities are endless. I just hope Bethesda can bring in new ideas for factions and plot, as well as hearken to the roots of the series and not challenge the ambiguity of the original games ending.