My thought is that they will be releasing new mage classes in 2.0, one of which will specialize in water, light, and dark magic. Personally, I'd bet that Arcanist is being re-design with those spells, plus debuffs in mind. We need a good DoT / Debuffer class in the game.
Again, pure speculation, but for as many people that are playing this game with all combat classes at level cap, they will HAVE to implement new classes for those players to stay engaged.