well, right now on the forums I see two idea's getting thrown around. one idea being that classes are unlocked in a FF:T type of way (20 gladiator, 10 conj = Paladin). the other idea I see, is that you have your base classes and that the "advance" jobs are actually just specializations within that base job (gladiator has paladin spec and dark knight spec depending on your play style) and right now that idea just looks like WoW to me...but with an armory system.