Thinking about Ultima a little harder I've come to the conclusion that we won't be getting the spell "Ultima" as a form of Ultima is already in the game: Proto Ultima and the Ultima from the Airship fight (most everyone already knows this). Ultima can be either a spell or a monster (potentially summonable, depending on game) but there hasn't been an instance of both the spell Ultima and the monster Ultima within the same final fantasy game before.

Can anyone think of such an instance? If not, then it's highly unlikely anything will be getting Ultima as a spell, aside from Summoner, which is even more unlikely.