I anticipate no new primals but instead actual clashes with Ascians.
Though Alexander seems likely as a primal post-3.0. The new expansion areas will likely have their own set of them, or completely focus on something like Alexander.
But I get the feeling we're ramping up for the Ascians and Zodiark. I imagine one of the final battles of the Ascian arc (which may be YEARS off) will be against all 12-ish of them simultaneously.