Who says that would even happen? I'd imagine if the games were to be remade for 3DS, the development duties would be handled by Matrix Software since they developed the remakes of III, IV, IV:The After Years and then made The Four Heroes of Light.
I, personally, love the art in Dissidia. I'm a huge fan of Amano's work, but I can't see it working in in-game graphics. Nomura did a good job of keeping Amano's work intact and making them into something that could be made into a videogame model.