I think its likely they're going to make Green Mage more like the D&D Druids if I had to guess to make it fit into this game, it wouldn't make sense to suddenly have another healer job.

and I guess this would be our 5th Magical Ranged DPS, maybe they felt that Blue Mage was too separate from the other three.

and the one in the trailer might likely be the physical ranged DPS (maybe, still doesn't explain his melee weapon).