1. 'Light' Type, it looks like it's in an egg this could be some sort of new type that would include all the fairy pokemon. 2. Flying Type, right underneath Sylveon is a little wing type shape in the design. 3. Bug Type, the design looks like a bug wing (doubt this one though).
I think many here have good evidence that it could be flying type. Otherwise, I would guess we're finally getting a normal evolution for the normal-type Evee. Pink is very often associated with the normal type in Pokemon, as is cuteness (which, with all the bows and ribbons in Sylveon's design, it's definitely trying to play up the "cuteness" factor more than the others).
I doubt it's a new type, another psychic type, or a dual type. There's just no precedence for those guesses, nor does anything about Sylveon's design suggest one of those things. The "love type" fears are especially unfounded, since it's based on the simple fact that the symbol is pink. Also, what would a "love" type do? It would either act very much like Psychic or be a type completely devoted to supports/charms... which would kinda suck. It might make sense for the meta, but it would make for many incredibly useless Pokemon in story mode. And they don't need a new type to make Pokemon that easily fill "support" roles.