I hope they do, as much as I want FFVI to be remade at long last. (Not counting the GBA version with the new translation and scaled down graphics and difficulty, which I already own.)
Final Fantasy V would be a great one to add some dialog to, flesh out the world(s) a bit in terms of detail, and the job system really is brilliant. Not to mention the combat is Active Time Battle, unlike FF III.
Also, FFVI would probably end up on the DS2 that way, and I think I'd rather see it with slightly less blocky character designs, as much as I loved FF IV DS.