I doubt online petitions even get read by anyone with the power to change anything. Also, I guess there wont be enough people to sign it anyways.
That said, it would be pretty cool if they did release FFIII on the PS.
And PS one games arent even looked upon anymore, so It would of had to be released on the PS2. Meaning it would have to of gone through alot of work to go up toi those standards, and Square didnt intentionally want that. So heading it to the DS was a good move.