AC was a sequal to 7. X-2 was a sequal to X. So I don't think X needs a movie when it already got its sequal. And I think 8 tired up the lose ends nicely in its ending. 7 got a sequal not only because of its popularity, but because of all the possibility its ending left. Nothing was diffinitively tied up. It was all open-ended and up to interpretation. So I think out of those options the only likely one would have to be X-2 as I can't speak on that since I haven't played it. But I think the FFX franchise might have already lived its life anyway.

FFV got a sequal anime of sorts. I'd settle for an anime about everyday life after FF6. I liked those characters. But again, things were pretty well tied up in that ending too so I don't expect it'd be too dramatic.