Skyrim is by far one of the BEST RPG games I've played and it's so difficult to resist! Although, I have wondered about Skyrim further into 2012 and if there will be any sort of new patches or expansions that will be implemented. Perhaps expansion of the world map and new areas and major quests lines?
Judging by typical expansions- for games like Morrowind, Oblivion, FO3, NV (which isn't Bethesda, but is so similar I wouldn't be surprised that it influened TESV)- What we'll probably see is a journey somewhere else with it's own separate world map. Maybe to some island in another part of Tamriel, or into another Daedric Realm.
That said, we'll probably see at least one expansion that remains in Skyrim and gives access to some sort of special player house with extra amenities (arcane enchanter, smelter, smithing table, alchemy table, ingredient garden, atronach workshop, ore transmuter, etc) since those seem to be common as well.