I think there is going to be a secondary quest line involving Falmer. There are several shots in the trailer depicting really icy conditions - including the part where the dragon plunges into the icy lake, but there is one where a finishing move in first person is done against a Falmer. At first I thought this was a vampire and it happened quite fast, but upon closer inspection - that was definitely a falmer.
The part where the player's character is a flying vampire lord doing a shout like thing in an underground location has several distinct falmer structures - the tunnels they use, their huts, etc.,
Oh god no, no, no no! I'm an atheist but at the moment I'm praying to every deity I've ever heard of, that there is absolutely no Falmer content in this dlc.
This dlc is vampire centric, think about it! You know how the Bethesda writers are. They'll either turn the Falmer into a ridiculous vampiric race of mer, because hey, this is a vampire dlc, or have them join forces with the vampires. Either way we'd just have to kill some more Falmer and would get absolutely no story.