Let's look at this rationally.

Sylveon, in the new trailer seems to be using the move Cosmic Power. Look at the Pokémon that can currently learn Cosmic Power by level up (no Pokémon can learn it by breeding). They all have something to do with one of two things:

>An innate mystical psychic power owing to its Psychic typing.
>Space.

The move description reads:

>"The user absorbs a mystical power from space to raise its Defense and Sp. Def stats."

Considering that it seems likely this will be Sylveon's main ability, I think we're getting a new type. Just because this kind of "otherworldly" ability doesn't quite fit an existing type that isn't Psychic (taken by Espeon). If Sylveon was Flying, Normal, Dragon or Bug, then what about its design would make the developers want to give it this kind of ability? What's the reasoning behind this? Unless Sylveon is the mascot for the newly introduced type, I don't see any other reason to give it such specific abilities that don't match an existing type.

It helps as well that Yveltal and Xerneas' types are still unknown. Whilst it's a bit easier to guess what they COULD be...there's still some speculation surrounding them. They also seem to take from Norse mythology, which is well known to talk about other worlds.

Note, I'm not saying we're getting a specific Cosmic, Light or Fairy type or whatever else fans have come up with. I'm just saying that it's a distinct possibility that Sylveon will represent a type that has these kind of otherworldly abilities. Which is why the concept behind this particular Pokémon could be fairies

I'd also like to point out that I was a firm believer in the Flying type theory before this trailer. And no, that symbol isn't a feather, it's Sylveon's ear.