Dont expect any new landmass DLC's and certainly nothing the size of shivering isles. Dragonborn was the *big* landmass DLC, it was the point lookout and S.I of Skyrim. Beth have stated that they'd rather release more smaller sized DLC's than one massive one.
So just had to clear the air, I see a lot of people expecting half of Hammerfell next DLC, or the entire summerset isles. Well its not going to happen. Expect some filler DLC and a new dungeon or two taking place in the current game world.