I think Square would be pretty apprehensive about a new film given how badly The Spirits Within performed. Which is a shame, because that could've been a real landmark both for Square and for animated films in general.

Having said that, I agree with Big D. If they were to make a new film, it'd be better to have a self-contained story rather than a spin-off or adaptation of one of the games. Having said that, if a film was made of FFVII, then I'm sure the crowds would be drawn in to see that because it's a popular game, but I personally would rather they didn't. Square's emphasis these days seems to be on previous games (through the remakes for the DS, the whole FFVII 'franchise', etc) and so I think it'd be better if they did something new for a hypothetical film, rather than a rehash of something they've already done.