Skyrim's first piece of downloadable content, Dawnguard, will be out this (northern) summer for Xbox 360, publisher Bethesda said today.
Dawnguard, which Bethesda trademarked earlier this year, could refer to a museum located in the city of Dawnstar that is dedicated to the "Order of the Mythic Dawn."
A recent patch also hinted at potential future content such as frost elves and crossbow weapons.
Bethesda has promised that Skyrim's DLC will feel like expansion packs, so it's safe to expect a hefty amount of content in this release.
Although Bethesda has only announced Dawnguard for Xbox 360 so far, previous so-called "console exclusive" downloadable content from the publisher has made its way to other platforms on future dates. In other words, it could just be lagging on the PlayStation 3.
Update: Bethesda has confirmed that Dawnguard is a timed exclusive for the Xbox 360.
Dawnguard [Bethesda Blog]