From a purely practical standpoint, nothing like this would ever happen. The only alpha predator that has ever spread over a vast area of the planet has been humans, and thats because we eat everything. In most eco systems, the number of alpha predators is very small compared to every other type of creatures in that eco system. This is a balancing act. If something were to come along and replace humans as the dominant alpha predator on the planet, they would have to do so completely. At this point we pretty much out number everything that would be able to do it short of a virus that killed us near instantly. If vampires were to spread across the world, they would run out of food really quickly. That's primarily why in most stories, vampire numbers are small and contained. Even in the White Wolf games, they say humans out number vampires 100,000 to 1. Even without super speed, strength, and toughness, 100,000 to 1, you loose.