There's no sequel planned, and no basis for one. If anything, it would be a prequel, but I doubt that'll happen either. There's just no market for it. X still had the hype, it was a new game and they made a sequel very soon after. With VII's movie sequel, they have the fact that it's their best selling game to back it up. VI, while awesome and my personal favorite, doesnt have the draw, at least not in the eyes of marketers.