It would make more sense for FF9 to be the next Omega thing.

FF5, FF6, and FF9 share very close and common themes with each other, similar levels of technology. FF7 and FF8 jump way up in tech and they are just in a completely different style.

That and FF7 is already done to death. Really, now.

I'd look forward to fighting some of FF9's nasties.

Though now that I think about it... they could also go FF4 too.