I'm hoping for a dragon type, still, but I dunno whether I expect it to happen. They've so far come out in pairs since the first three, but Sylveon has had so much hype and has, as was said, essentially become Gen 6's mascot Pokemon. There's just too much focus on Sylveon, I think, but alternatively, another eeveelution could be planned for a sneaky surprise. Please let it be that. D:
I don't think there will be another one. As you may know there is a Pikachu short for the latest movie which is about Eevee and its evolutions. If these was another one I think they would have included it there aswell.
As mentioned above, Sylveon has become something of a "mascot" for
Pokemon X and Y/Generation 6, so I'm doubtful of another Eeveelution being introduced... Not to mention that the recent special included Sylveon and the pre-Generation 6 Eeveelutions, so seeing a 'secret' Eeveelution being revealed while being absent from the first movie special with strong ties to XY would just seem weird.
However, I'm still holding out hope! A
Dragon-type Eeveelution is probably my most desired at the moment (if not in XY, then at some future
Pokemon game/generation), so that all Pokemon types that were considered "Special" prior to Generation 4 will have finally received Eeveelutions. Plus, it would likely look cool! :D After that, a
Fighting-type Eeveelution would be my next choice (in Generation 6 or the future), simply because the purported name
"Champeon" is so wonderfully punny!
I'm still anticipating a Light-type at some point (possibly), so a
secret Light-type counterpart to Sylveon could prove to be interesting, if such a Pokemon
does debut in XY...
I originally wanted Sylveon to be Flying-type (due to the name IMO suggesting
sylphs/air elementals, or something of the sort), but now that the name "Sylveon" has been taken, I'm not sure if there would be a suitable 'Flying-type' name left for such an Eeveelution.
Dragon, Bug, Poison, Flying, Rock, Ground, Fighting, Steel, and Ghost...and if consider [S-HIGHLIGHT]the ??? type[/S-HIGHLIGHT] then sure.
Hope they at least have 2 more, or all, if that's even legal. But those are the types that are left. I'm rooting for Steel, Ghost, and Dragon.
LOL; it would have been amusing if Sylveon was actually revealed to be ???-type (honestly, I was getting overwhelmed with its type speculaton; and slightly irritated as well because the type's identity was held out from us for months)....all that pre-reveal guessing, only for us to be left 'forever guessing'. XD