EDIT: after a little bit of research, i'm now convinced that Sylveon will be probably a Normal Type pokemon... i'm not happy with that, but all the clues point in that direction..
Fairy references are in all the names of Sylveon, and though it can be argued that they reference Sylph or Sylvia Butterflies, the reality is that it's a very stretching interpretation for an eeveelution, which usually have very straight-forward name connection with their type. Ninfia just reference mythological nymphs and the same applies for Sylveon. But the German name is the key in this case: FEELINARA.
There is no reference at all to butterflies or air-related themes, but it is instead a clever pun from Feline and Fee (fairy in german). We know that fairy like pokemon like clefairy and gigglypuff are normal so, although I prefer to believe in the (unlikely) introduction of a new type rather than in the addition of a generic normal eeveelution, i'm rather sure that Sylveon is just a Normal type.
Another clue is that it is shown using normal typed moves in the trailer, but i have to say that the most convincing evidence is that the new games will be probably set in a France-inspired region: this explains the graceful appearance, the fashion-like features (ribbons) and also the Nymph references, since Nymph statues and depictions were extremely common in Versailles and in Royal France in general!
I have to say that explained this way, the idea of Normal eeveelution doesn't seems all that bad :3
I was quite intrigued lately by the debate on Sylveon. Not so much about the design, that in my opinion -at the moment- seems strangely ok (I'm talking of the others VI gen pkmn too), but about its TYPE...
At first, when it was still called Ninfia, I genuinely thought it might be an extravagant BUG Pokemon.. those butterfly-like ribbons ... glassy eyes ... and the name that seemed to come from Nymph (in the "insect stage" sense)..
But might seem also a stylish flying pkmn....also i still had not abandoned the idea of the normal type, but Ninfia seemed so little eevee-ish!
Then other information leaked and add even more confusion: Ninfia is the lightest eeveelution ... it's a flying Pokemon then? No it's dragon.. no, Ghost ... I have seen every possible type attributed to Sylveon, but the truth is that this Pokemon does not seem to belong to any of them!
Is for this reason that the introduction of a new type (Magic? Fairy), which seemed very unlikely before, began to emerge in my mind...
Then at the end came the English name: Sylveon!
Since all eeveelutions contain information about their type in their name, this clue isn't to be taken lightly ... sure, it could still come from Sylph, a nymph of the air, and then be Flying, but it is unlikely! In all probability Sylveon comes from Sylvan, which is the name of the spirits of the woods, or more generally of the mythical Nymphs (oh it was in this sense then!)
In short, I think there is the very real possibility that a new type Fairy / Magic can really be introduced!
If this will happen I'll be very pleased, since many fans (me among them) had already forseen the introduction of this type!!!
What do you think?
P.S. If Sylveon proves to be a Normal or Flying at the end, I don't deny that I will be a little disappointed .. in terms of design and regarding its name, it doesn't really fit any of the dear old types!
I noticed that my idea about Sylveon type changes every 15 minutes or so :/