Its almost certainly just a rumor, Though Square have been revisiting there older games more recently. If they did a remake I would expect more then the re-releases they do constantly, Updated Graphics but with the old feel. It would be intresting to see them finish the areas they didn't in FFVI.

I think this rumor stems from the sprites they made for the ps2 or ps3 or whatever it was to show off its new graphics, like the FFVII Intro remake for the ps3 graphic show.