I think dual leadered Italy would make a lot of sense, (though like you i don't see italy in the trailer). someone somewhere here said A florence/venice like athens/sparta dichotomy could make great sense in this game. I don't buy that 'no new city states' means no korea. they clearly just switched up a city state to bandar brunei to make room for Indonesia. Its nothing really to find another city to fit in a particular theme if its time to graduate Seoul (or Lisbon, Amsterdam, Toronto, Carthage, etc.) They did this in Civ V often.
Thus my list is: Mongolia, Korea, Dutch, Inca, Italy (Florence/Venice), Sioux, Portugal, and Ottomans.