User blog comment:Blood Reaper/Skyrim Dawnguard Trailer/@comment-4353017-20120601103506/@comment-76.14.103.94-20120601180305

The whole destruction of the food chain thing is a good point to how their plan isn't the most thought out, but in the trailer it does hint at vampires having the ability to consume the souls of the dead. That could be one way they will survive once they run out of blood.