Each of these civs could be the next one

Balts
Armenians
Khorasimians
Afghans
Flemish
Tibetans
Chumu
Muisca
Kongo
Zimbabwe
Benin
Hausa
Alans
Cumans
Vandals
Swahili
Uzbeks
Somalians
Kurds
Frisians/Dutch
Siamese
Bornu
Zapotecs

And the ones that are techincally already part of a civ

Bulgars
Poles
Bohemians
Omani
Egyptians
Serbs
Normans
Jurchens
Swiss
Tamil