It looked pretty, but I fear it may prove to be more flash than substance. When you start with a society of vampires milking the humans like cattle for their blood, you'd think they would have, very early on, established a way to breed humans for continued consumption. They make no reference to a plague wiping out the humans. So it seems to boil down to either some info not in the trailer, or they created a convoluted starting point to justify the movie
The vampires are created by a plague, ala I Am Legend. This means the their numbers increased beyond the pool of resources available to them quite quickly (Evidently vampires outnumber humans 19 to 1). Keep in mind it's only 10 years in the future. Humans breed slowly.
Plus, the vampires are essentially mentally human, and if there is one thing humans often are with their resources, it is short sighted. It appears the film is an allegory about this sort of thing.
Early reviews of this film are very good, and apparently they were going for a deliberately early John Carpenter vibe - which is great! I'll be seeing it.