ケンジ
僕は準備完了しています!
Legendaries and a couple of Specific Pokémon manage to retain their original name, all the rest get revealed and change their name from Japanese to English. Given how every Eeveelution have different names between Japanese and English, I'm pretty sure Ninfia is the Japanese name, so when it translates to English what ever they put in the front it must end with an eon. However based on Leafeon and Glacion's Japanese/English name, their is a high chance that Ninfia's English name will be Ninfeon.
Now about evolving it, I think it will a be a new Item that will be introduced in Gen VI that specifically evolves Eevee into this new Eeveelution. I guess they could use a currently known item but recent Eeveelutions don't require the use of items to evolve so it doesn't necessarily need an item to evolve.
Finally about it's type, I am certain it is a type that hasn't been used for Eeveelutions so far and from the looks of it, Ninfia looks like a Flying Type. Any other Type that hasn't been used just doesn't suit Ninfia's looks and because it looks elegant Flying fits it perfectly. I guess it could be a Normal type as well but with other Eeveelutions being Pure Types I highly doubt this one will be a duel type and I also doubt it will be a completely new type.
Either way I like the looks of Ninfia and I it will be a nice addition to my collection, who knows it may be on par with my favorite Eeveelution which is Espeon.
Ninfia IS the Japanese name yeah.
Looking at Ninfia, I really really REALLY doubt that it's a new item. It will make use of the current item, the Prism Scale. Here's a picture of that scale, it resembles the patterns on Ninfeon.