I still have hopes for the Parasite Eve Remake that was rumored a while back.
But I would put my hopes on something from Enix rather than Square. Generally, Enix is a much better developer than Square, although they aren't as appreciated in the west. I would REALLY like to see something from Enix on GameCube.
But no, I really don't want to speculate, as that has a tendency to start rumors and crap. I will just say that I think that there's definately another game coming from Square-Enix.