Seeing as the revealed factions fit with the roman expansion, as usual, I'd say the Ptolemaioi are a given. While the other slot must be something in Asia Minor or the Caucasus, I'd say Pontos or Hayasdan are the most likely, due to the amount of sources and Mithridates/Tigranes lore. Plus the apparent disdain for the Seleukidai by CA XD

I'd prefer Pahlava, but with the other factions, having such a lonely spot in the east would be terrible...
Honestly I'm wondering how far east the map will really go...

As for DLCs, I can see cultures packs: hellenistic DLC, arabic DLC, nomadic DLC etc...