I'm not sure if this has come up as speculation before, I couldn't find it though, so I'm going to put it up!
Now, in the past, whenever additional Eeveelutions have been released, it has been in twos. One always having an advantage over the other, Glaceon and Leafeon, Umbreon and Espeon. So, with this in mind, does this mean we are in store for a second Eeveelution, along with Sylveon, in Generation VI?
Since all we know about the Fairy type at the moment is its 2x effectiveness against Dragon, this means a Dragon type Eeeveelution may even be a possibility, but that does seem unlikely to me. When Fairy's other type effectiveness's are revealed, another type may seem more likely, possibly Ghost?