I can't find the source but didn't they say they wouldn't just be adding to the game with dlc but also improving on already existing features?

I remember seeing that also, it's a bit like a patch along with some game DLC, might as well call it update 1.6 if it includes some patches.

True but I don't think it just means bugs

DLC means content, features are content. Some DLCs add features, some just add quests.

We have a DLC Speculation thread, please use that.

http://www.gamesas.com/topic/1372881-dawnguard-and-future-dlc-discussion-thread-27/