I don't think the Moon Stone will be used for the Sylveon evo. In Pokémon XD Gale of Darkness, you can get items called the Sun Shard or the Moon Shard which allows your Eevee to evolve to Espeon and Umbreon respectively. I'm thinking these items are somewhat related to the Sun and Moon Stones...but that's just a theory. A Game... *bricked by MatPat* OW!! Okay, I won't steal your schtick!
Personally, I'm leaning towards Amie as the Sylveon evo method. It seems the most likely since I would not be surprised that they'd implement a new feature like that.
The fourth wall has shattered... Heroes of Arcadia - http://www.fanfiction.net/~anthonybault
How do you guys think Eevee evolves into Sylveon. Most likely Moon Stone.
Most likely not.
Gen I Eeveelutions: Evolution stones. Introduced in Gen I. Gen II Eeveelutions: Day/Night + Happiness. Introduced in Gen II. Gen IV Eeveelutions: Location-based. Introduced in Gen IV.
To be entirely fair, new evolutions aren't always tied to new mechanics, just as long as it's something that couldn't happen in previous games. A lot of Pokemon gain new evolutions by holding/using new items, even when item-based evolution had already been done. As long as it's not something that causes people to ask, "How come my Eevee didn't evolve into Sylveon when I tried to use a Moon Stone back in Red?"
Socran's Razor: "Never attribute to massive stupidity by someone else, what could be explained by a tiny bit of stupidity on your own part."