There's plenty of clues about what the Skyrim DLC may be about buried in some Skyrim patch filenames.
Dragon mounts, Morrowind, and Daedrics, oh my!
These are just a few of the wild rumors floating about on the Internet about what Skyrim's DLC could be about.
However, a BethSoft forum user found some concrete evidence as to what the DLC's contents could actually be after scanning the Skyrim 1.5.26 patch files, revealing the following filenames (among others):
Yeah... I spent, nearly, the entirety of December and January locked into Skyrim... It is one of the main reasons I am so far behind right now!!!!! I played through the game 4 times, twice maxing my level, before forcing myself to give it up! The last game that did that to me was Oblivion!