Sephiroth 3D: I really doubt that it would work. There was discussion about petitions and stuff _long_ time ago (long enough that I couldn't find it with search), where halkun expressed his views on Square's decision making process. I agree with it completely, you can't convince company of that size into making a port that their own research has deemed as having very bad profitability
It's about money, after all. Of course, if you could get tens of thousands of people to send letters, it might have some effect (as in; they _might_ re-evaluate the profitability), otherwise it's pretty much lost cause, IMHO.
The Movie makes it even less likely, causing Square to make a net loss for the first year ever is pretty strong incentive to stick to things that are known to be profitable. And one can't really downplay Sony's part in it either.