As we have only three Civs to go and my last guess was a total failure I try to correct myself.
Clues:
1. We have a pattern 4 new Civs 4 returning ones
2. We have a geographical pattern of DLC
3. We have a Venice City State (let's assume it is a replacement of the new Civilization - can be just a new CS as well)
4. We have Central/South America, Africa, and Europe already covered.
5. We have a leak of Kubai Khan and Vietnam (let's assume it is the thing)
This makes only two spots. One for a new one and one for returning one SA, EU, Africa, and Asia are covered.
One spot takes existing trade CS.
Hunza is out with South America, Lisbon is out with Europe, Zanzibar is out with Africa, Bandar Brunei is out with Asia. We left with: Antioch (Middle East), Cahokia (NA), Muscat (Middle East). The strongest contender here is Cahokia with The Mississippians
This means there is only one left spot for a returning Civ outside the Americas, Eastern Asia, Africa and Europa. We are left with Assyria, Babylon, and Hittites.
So the final list of NFP Civs is: The Maya, Gran Colombia, Etiopia, Gauls, Byzantium, Vietnam, Mississippians and Babylon/Assyria. (if Venice CS is a replacement and Vietnam leak is true)