There have been plenty of rumors, and even some concrete evidence.
But Fallout 4 isn't official and probably won't be for quite some time. Bethesda director Todd Howard told RockPaperShotgun that the team isn't prepared to announce anything just yet.
"We don't [have a timeframe for our next game announcement]. But I think it's gonna be a while."
Howard added that they've "gotten fairly used to all the questions and curiosity over the years," and he understands that "everyone wants information." But it's clear that the team is still in a semi-building phase, as Howard says they're trying to figure out which of their ideas will "stick." Only then will they release some details about the project, which we all assume is Fallout 4 set in a post-apocalyptic Boston.
As for that Boston rumor, Howard had nothing to say. So, guess franchise fans are just gonna have to be patient.
Related Game(s): Fallout 4