All of them!!! /s
Jokes aside, before they think of making more dlcs they should fix all the bugs, glitches, writing, etc. ACT 3 in particular.
After that adding DLCs that add more subclassess, races, maybe expanding a region or adding a new one will be enough.
Before that though, I want mod tools ASAP. Mods will give this game as much life as Skyrim has got, well, maybe a bit less.