I think we'll see
1. Portugal
The last major colonial power they haven't implemented (besides Italy, though Portugal was much, much larger)
2. Holy Roman Empire
One of the last historic European empires that isn't in the game.
3. Tibetan Empire
Geographically and culturally quite distinct from China, certainly not any more obscure than Polynesia or Songhai.
4. Mexico or Canada
I think one of them is bound to make it.
5. Assyrian Empire
Or maybe Israel? There's a lot of civs around the Middle East already so I'm not too sure about this one.
6. Brazil/Argentina/Chile
This one is for sure, they need some South American representation
7. Another African civ
Probably the Zulu like people have been saying, or maybe something else. Africa actually has quite a few civs in Civ5 (Ethiopia, Carthage, Songhai, Egypt) so they might go for something more distinct.
Anyways, I think the criteria is just that the civ is unique enough to fit into the game. Many civs already in the game were only "empires" by name (Korea, Ethiopia, Celtica etc...) and quite a few overlap each other in terms of geography (Persia, Arabia, Ottomans, and Babylon all occupy the same general area).
1. Portugal
The last major colonial power they haven't implemented (besides Italy, though Portugal was much, much larger)
2. Holy Roman Empire
One of the last historic European empires that isn't in the game.
3. Tibetan Empire
Geographically and culturally quite distinct from China, certainly not any more obscure than Polynesia or Songhai.
4. Mexico or Canada
I think one of them is bound to make it.
5. Assyrian Empire
Or maybe Israel? There's a lot of civs around the Middle East already so I'm not too sure about this one.
6. Brazil/Argentina/Chile
This one is for sure, they need some South American representation
7. Another African civ
Probably the Zulu like people have been saying, or maybe something else. Africa actually has quite a few civs in Civ5 (Ethiopia, Carthage, Songhai, Egypt) so they might go for something more distinct.
Anyways, I think the criteria is just that the civ is unique enough to fit into the game. Many civs already in the game were only "empires" by name (Korea, Ethiopia, Celtica etc...) and quite a few overlap each other in terms of geography (Persia, Arabia, Ottomans, and Babylon all occupy the same general area).