So what would be your "out of left field" guesses? The darkhorses?
I could see the following
1. Israel (After years of begging, the Polish finally got their civ - Israel would bring sales as well particularly in the pro-Israel west where the game sells)
2. Belgium (Scramble for Africa scenario, already has 2 city states, another European civ, etc.)
3. Italy (I don't see it happening, but it is reasonable to put them in the dark horse category)
4. Inuit (A fan favorite here in these forums and after seeing Polynesia, it is a potential choice)
5. Swahili/Zimbabwe/Benin/etc. Most people are rightfully guessing Kongo and Zulu, but with the Scramble for Africa scenario I wouldn't be surprised if we got another African civ as well
6. Gran Colombia - (Would fit into the New Worldish kind of theme that seems to be going on)
7. Khazars (Continuing on the diplomatic, religious, and horse based cultures that are traditional in Civ. It would be a somewhat central Asian civ too to fill up more of the map)
8. Vatican/Papal States. Would cover the in between from non Italian city states and the Italian Peninsula. Has historically acted as a huge vehicle for diplomacy and in past civ games has been the alternative for a "World Congress" (Apostolic Palace or even somewhat arguable the into the ren. scenario from GK). Wide religious influence and would be less controversial than an Israel pick, pending when the civs were designed could fit well considering the recent resignation of Benedict/appointment of Francis I
Those are my left field potentials