Well, that little teaser from Bethesda is indeed a new DLC for Elder Scrolls V: Skyrim, and it's called Dragonborn. It seems like this DLC is focused on the history of the Dragonborns, and the picture above is apparently the first dragonborn. Oh, and dragon mounts! Check the trailer below.
The Dragonborn DLC will cost you 1600 MS point (20$) and will be available in Xbox Live on December 4. Just like past DLC's, the Xbox 360 gets first dibs on the content, no info yet when it will be released in other platforms.
[Source: Bethesda Blog]