FFVII Crossover?

[Greven]

I NEED Sephiroth's clothes.

I remember reading somewhere (Koji? Yoshi?) hinting they would probably make a collaborative event with another Final Fantasy in the future, but can't find it!
SOMEBODY HELP ME FIND IT!!! >o<

(I think it was at one of the Fanfests)

Dunno where but I remember it as well. Though it could be anything.