It really depends on what they do with Red Mage actually. I mean fencing is done face to face so I think RDM has a high chance of being a tank. If RDM gets a gunblade and goes the Mystic Knight route we could possibly see Samurai tank.

Still though I think our current tanks need more work, and during 4.0 lets push for a Beast Master or shape shifting tank job for 5.0.