I wouldn't say its so unlikely. If FFXI is anything to go by, they introduced at least one entirely new class--Puppetmaster; allowed players to be a classic NPC class for the first time--Corsair(Pirate!); resurrected a job that hadn't been used since FFIII--scholar, and also brought back a job that was only ever used in FFV--Rune Fencer (Mystic Knight).
So I'd say there's precedent for a new job, or seldom used job, being added to the game!![]()