I've accepted that they will eventually have to stop with adding new jobs and plan on playing as long as new raids, dungeons, and xpacs keep coming. FF has all sorts of great and fantastic jobs across all the games and the various universes, but I'm sure that many of them are so close to one another that it would not translate well into an MMO.

One thing I would personally like to see if they decide to adding entirely new jobs, is advancement of already established jobs. Kinda like what we have at level 30 for many of our current jobs. Some ideas would be to see our Mages become Wizards, PLD becoming Knight/Templar/Holy PLD. Not complete overhauls, but perhaps some aesthetic changes combined with stronger and more flashy moves.