seasnake
Conquistador
So, now we know that Israel, like Portugal, won't be in (as Jerusalem is in the game).
So that further shortens our list of possible civilizations. Here are my guesses (in order of the likeliness I think they have of being in the expansion):
1. Zulu
2. Sumeria
3. Hittites
4. Ethiopia
5. Austria
6. Assyria
7. Sioux
8. Poland
9. Hungary
10. Brazil
11. Khmer
12. Mali
13. Phoenicia
I'd say Mali is less likely than all of those given that Songhai/Mali is very similar. However, I do like the rest of your list of likely candidates. I'd almost move Khmer up given the focus on religion of this new pack. I think Ehtiopia is now a lock, Khmer is relatively likely.
I also have been thinking that there's one civ that may be coming in given the Gods and Kings title, and that's the Franks. Charlemagne and the Franks would fit the goals of this expansion, and they have two ready UUs (Franciscan Axe Thrower and Halberd infantry).