Given the arrival of Krile in 3.1 and the reveal that she has a new, unique weapon type (a crystal ball) I'm willing to bet her job may eventually be playable.
As far as 4.0 is concerned though I'm fairly certain we'll be liberating the conquered nations of Ala'Mhigo and Doma in preparation for 5.0 being the counter-attack on Garlemald. SAM and BLU are definite contenders there but I know Yoshi also wants to get RDM in at some point. It's hard to guess to be honest since they can so easily rewrite the lore of jobs to fit any new culture they add.