Bethesda is laying out the details for their plans post launch of Fallout 4. Following some similar paths as Skyrim, Bethesda will be updating the core game with both fixes and new features.
As well as past games, DLC will be a big part of their plan and for the first time, they are offering a Season Pass for $30 to net you all the DLCs. They don't have details on how many DLCs there will be, but history says there will be at least three to pick up. That would net you some good savings if you're one to buy all the DLC for Bethesda games. They are saying past DLCs have averaged $40, but there could be more for Fallout 4.
Also the Creation Kit will be coming next year and will allow you to create mods for the PC, Xbox One, and eventually the PlayStation 4.