There are rumors that Fallout 4 will be set in Boston. They're incredibly unsubstantiated--they come from a random poster on a message board--and the game doesn't even officially exist, but it's such an awesome idea that I want to take it seriously and I want it to be true.
According to the reddit commenter:
"Fallout 4 will take place in Boston. In case you haven't heard, Bethesda has recently been scoping out and researching Boston. They also have a strong connection to MIT. I may or may not be an MIT employee. But that's really all I can say for fear of losing my job. I am telling you it will take place in Boston."
Here's other evidence, from the Fallout universe itself, from Gamespot:
'The Commonwealth' was referenced in 2008's Fallout 3. Four real-world states in the US categorize themselves as Commonwealths: Pennsylvania, Kentucky, Virginia, and Massachusetts. Bethesda lead designer Emil Pagliarulo told 1UP in 2009 that the Commonwealth reference in Fallout 3 was in fact speaking about Massachusetts, not any of the other three states.
Also, both Fallout 3 and New Vegas featured references to an "Institute" that was in one of the commonwealths. The speculation is that this is a reference to MIT, as opposed to, say, The Kentucky Institute of Technology, which I totally made up.
Bethesda says they don't comment on rumor and speculation, but that shouldn't stop you from commenting on rumor and speculation! Use our comment section if you wanna.