I don't think most people want to become a Summoner becasue of 3.0 changes it just stops players from changing to Black Mage. There is nothing to summon right now except Hydaelyn since the Primals are nothing more than conjurations within the mind of the person summoning it so summoning a primal is would be more of a White Mage ability since they have the conjuring spell line. If I had to guess the next spells we get will be spells based around Calling since we already have an Evoker based spell with Dreadwyrm Trance.