A Reddit user known as derptemp6698, who previously leaked info about the Mass Effect 3 multiplayer DLC's, and was then proved correct, has claimed to know what Bethesda's next Skyrim DLC is all about. He writes:

"Hearthfire™, the next official game-add on for The Elder Scrolls V: Skyrim®, has arrived. For the first time in the Elder Scrolls universe, purchase land and build your own home from the ground up - from a simple one-room cottage to a sprawling compound complete with armory, alchemy laboratory, trophy room, and more! With Hearthfire, the possibilities of what you can build are endless."

Whether this turns out to be correct or not awaits to be seen. Considering Bethesda stated they wanted longer DLC more akin to expansion packs, this looks a little odd. Still, if it is part of something bigger I'm not complaining.

More details and discussion on the Bethesda forums.