Don't rule Blue Mage out just yet, it is still very possible for it to happen. Blue Mage doesn't have to have all Blue Magic only, just look at Red Mage with its fencing attacks. Also as far as learning Blue Magic: easily scripted into quests to learn new abilities.

Let us also not forget the subtle hint that Blue Mage is not forgotten: The Red Mage Minion's tooltip


P.S. I expect when we do get Blue Mage it will be a DPS job.