A) If it does well, there's nothing to stop SE from releasing it on Vita/3DS/Console Networks... all the assets will be there. Keep in mind, FFVI is the most popular FF game pre-FF7, once they have assets in place, they can port it around and print money!
B) Why should we assume it's going to be anything like the FFV remake? And would the graphic technology of the FFV remake be fine for FFVI? Sure it was a little more cartoony looking, but it didn't have to be. FFV is a pretty cartoony game itself, so I'm not convinced it didn't fit. FFVI is definitely not, so the sprite smoothing and detail increase could be used for more... sinister... means.
Come on people, we have been asking for an FFVI update for years, we finally get one, and even before we see screens we're complaining. Not cool.