Where would you like Fallout 4 to take place? Boston, judging the Commonwealth was mentioned in Fallout 3 or somewhere else, like in the Capital Wasteland again to see how it has changed? Or in Ronto where Lord Ashur mentioned in F3's DLC , The Pitt or somewhere way down south, in the deep south like Florida, Georgia, Missippi with a old Confederate theme? Or where?
Personally, I would like to see it either set in the Commonwealth, judging that's where it will be without all-the android thingie but instead you play as a BoS Soldier or someone who has a connection to the Railroad or someone from the railroad or somewhere like Ronto.
You can discuss about the plot, the characters, Three-Dog or something!!