IGN: Okay then, but if there was another sequel to an existing FINAL FANTASY game, which one would you like to work on most? (I myself would love to see a follow-up to IV or VI)
Kitase: Recently announced at TGS, a sequel to FFVII titled FINAL FANTASY VII: Advent Children is in the works as a visual piece (movie) and scheduled for release next year.
Tetsuya Nomura, who was the character designer on the original title, is on the project as the director. There are no plans at this time for FFIV or FFVI that you mentioned. Takashi Tokita was the director on FFIV so if he wants to, it could happen. I was the director on FFVI but right now, I have my hands full with FFVII: AC so it would be difficult.
Toriyama: Right now, I want to work on a new story so I don't have much interest, but I do like the worlds of FFVI and FFVII.
Thanks to IGN.
It appears unlikely since they're most likely working on FINAL FANTASY X-3 next but they could do a sequel afterwards for VI or VII when they're eventually remade, like what occurred with The After Years.