Speaking of Fallout 5, are there are any hints about the game's next location, the way the Commonwealth was hinted at in FO3?
There's this mini-game:
That's San Francisco, Seattle, New Vegas, Mount Rushmore, Boston, St. Louis, Washington and New York.
Out of the ones above, and assuming there could be a hint in the first place, only Seattle, Mount Rushmore, and New York haven't appeared in a Fallout game. I don't think they'll make Fallout: South Dakota, so we can rule that one out.
San Francisco is more heavily mentioned than the rest (so far, at least), as it appears in Kellogg's memories. I think that's a strong candidate if Obsidian gets another shot, even if it was in FO2 already. Seattle is more in line with the Bethesda locations, but it's also much less iconic and smaller than the rest. St. Louis sounds more like DLC material to me.
Personally I think Bethesda will finally make the move to New York. They've been using increasingly larger territories, but New York is by far the absolute largest. I suspect the devs themselves must get excited with the idea of making Fallout in NYC, and since they can only make TES or Fallout at a time, if they don't it in FO5, they must think perhaps they never will. I mean, at this rate, Fallout 6 will come out in 2024-25.
There is no hint like the Replicated Man quest in FO3, though. All of the factions mentioned in the game so far are already known or from the Commonwealth alone.