Beastmaster (Trainer) pre-setup
If you think about the way they already have the game designed, and the current MO for doing our Chocobo's, the beastmaster is an obvious set forward from that.
Training Grounds - When they add a class, they add a pen like the Chcobo Stables.
Taming - I am sure I ain't the only one who has grinded leves for powerleveling DPS classes, and the leves at every level point have a mission to pacify creatures - so we have that mechanic.
Summoning - Could be tricky
Limits of Pets - This could work like the Chcobo where getting to lvl 10, then to go higher you have to feed it something for every lvl progression, but you loose a permenant pen place for keeping it. That way we can interchange our pets and it puts the job makeup on the player.
Interesting thoughts - 8 beastmasters going into Binding Coil (or Crystal Tower)...
With the buildup of this, I would expect that if they have already started it (enough evidence to say they have) this may be a mid 3.0 series to mid 4.0 series release.
I will say that there is enough in game evidence to say that the job is coming, only a question of when.