You will get a Vampire only event when Werewolves get their event, and everyone else gets their own event that for some reason excludes others from content.
Hope ZOS will create a good short story with some of the deities Anui-El / Auri-El, who appear before us from their mystical realms, and the story goes. They are quite creative in these stories. From lore perspective it isn't hard to create such content in mmo. Werewolves already have their event each time they gather a pack, transform and run around killing mobs. Being a WW is just much more entertaining.