It seems like we deal with a single Primal Incarnate in 10.0. We also know that there's some involvement of the underground in 10.1, possibly for a fire/earth ones? It looks like Primal Incarnates will be our main threat for next patches as well - 3 of them possibly escape the Vault of the Incarnates? --> all 4 of them have been locked there IIRC.
If that is the case, and based on what Ion said in MrGM's interview (grounded story and we most probably know the main villian by the end of 10.0), Galakrond seems to be a good candidate. There's a lot of talk around Galakrond to be honest.
Nevertheless it's either Murozond or Galakrond and that is out of question.