The DLCs for the FO series have been a bit hard to predict - at least for me.
It's been somewhat easier for the ES series, in that DLCs/expansions to the vanilla game either involve territories nearby or going to other dimensions/planes of existence. For instance: in Morrowind/ES3, we went to mainland Morrowind and Solstheim, which at the time was controlled by neighboring Skyrim. ES4 stayed in province for the first DLC and then took us to an Oblivion plane. Skyrim visited the remotest border regions of neighboring provinces (High Rock and Morrowind) and also took us to alternate planes.
But the FO DLC don't follow such neat and tidy patterns. In fact, I can't imagine a DLC for FO4 taking us to, say, New Vegas or Washington DC.
If the fan base had any influence on choices, I would love to head into New Hampshire and/or Vermont from FO4's boston and see some genuine, non-radioactive green mountain country.
Has anyone picked up on clues from Bethesda what they are thinking in terms of expansions to FO4?