User blog comment:Blood Reaper/Skyrim Dawnguard Trailer/@comment-3076045-20120531154155/@comment-4011214-20120531155339

Well, DLC is usually used to describe smaller downloadable content like weapon and armour packs. But judging from the price of Dawnguard (1600 MS points), I think it will be pretty big, like The Shivering Isles for Oblivion.

Hence 'game add-on'.