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'm not your bro, bro.
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.
Has anyone considered Poison as a possibility? OK, stupid question, I'm sure many people have considered it over the months of speculation...
But still, when I see pink, the first types that pop into my head are Psychic, Normal...and Poison. Maybe poison is normally more of a purple, but still, I could see it.
I just think it's odd that every other eeveelution is so obviously identifiable at a glance. Anyway, Poison probably isn't my guess, but I just thought I'd throw it out there. --- I summoned a baby to attract a lion. It didn't seem to work, so I tried a delicious baby. Regular baby ATE delicious baby. Horror....horror.~Gameplayingperson
From this, I will deduce that the shape of the background's they are each in doesn't matter. I can't see it being any type but a new type. I would guess a Fairy, Love, or Light type. --- 3DS FC: 3050-7585-1835