The Elder Scrolls V: Skyrim First DLC Named Dawnguard?

A DLC or an entirely new game?
CVG is reporting that ZeniMax Media, the Bethesda Softworks parent company, has filed a trademark for Dawnguard, a name that could be the title of an upcoming DLC expansion for The Elder Scrolls V: Skyrim. The trademark is for "computer game software for use with computers and video game consoles; downloadable computer game software offered via the internet and wireless devices".
CVG notes that the trademark bares a similarity in name to the Mythic Dawn Guards which appeared in The Elder Scrolls IV: Oblivion - it seems they are members of the Mythic Dawn cult, which worships Mehrunes Dagon, the daedric prince of destruction.