User blog comment:G0LD3NF1RE/Skyrim Dawnguard DLC/@comment-68.192.79.68-20120504002209/@comment-69.146.244.153-20120504025254

It would also be hard to bring an entire race back into the game effectively in a single DLC. It couldn't be insignificant enough, but perhaps over multiple DLC's? Probably not though...