Besides Alexander, I don't think they have any good creatures left that could be given Primal or elder primal status, except Pheonix. Diablos and Siren are just regular bosses. I think Fenrir is mentioned somewhere as an elder, but if diablos and Siren don't make the cut, I don't see much hope for anything else showing up as a Primal past Shiva.

That Said, nothing stopping them from adding in Cactuars and Tonberrys and such as "Primals" like they did Mooge King. But they really won't be official Primals, just more Ascian's playing around with different summoning techniques.

I just wonder who the other beast races worship if anything. The Qurin, Mamool Ja, Goblins, Gigas/Giants, Dragons, and maybe the Imps...