After more reading about, I am thinking a the moment that the new civs will probably be
1. the Spanish
2. the Arabs
3. the Mongols
+4. the Vikings or Scandinavians
5. the Celts
6. the Carthaginians/ or the Hebrews instead
7. the Inca
8. either Korea (for commercial reasons rather than achievement) or Indonesia
Personally, though, my euro-centrism makes me desire that we have:
1. the Spanish - created almost all Latin America, most powerful state in the world for a good few centuries
2. the Arabs - created Islam and territories extending from Spain too Indo-China, helped preserve Greek and Indian knowledge even if they didn't make many original contributions themselves
3. the Celts - invented ring-mail and had territories extending from Spain and Ireland to Asia Minor
4. the Scots - gave us, in many ways, television, telephone, penicillin, social sciences, geology, Marxism (Scottish enlightenment historiography), and was the most important centre of the European Enlightenment
5. the Scandinavians - we all know what the Vikings did, plus there is Gustavus Adolphus, Uppsala, Danish astronomy, Swedish film, etc
6. the Turks - cool addition, would like to play them against the Germans, and TAKE VIENNA
7. the Aborigines - if civ3 is about changing history, this is the ultimate civ to do this. A large historico-anthropological group perhaps closer to any other large group to "man, as he really is"
8. another balance civ, like the Indonesians Ethiopians or Inca