HanNorwood
.exe
imho:
99.9%: China, Japan, Egypt, America
Pretty Sure: Rome, France, England, Russia, Arabia, Ottomans, Germany, Greece, Persia
Probable: India, Aztec
Speculation: Native American, SE Asian, African
Reasoning:
Apart from the pretty much confirmed civs, all of the 2nd tier civs would be no brainers considering the history of the game, these are probably unlikely subject to change though something like Germany being replaced by Spain or France/Ottomans being released as a DLC in the following month along with a scenario is not beyond possibility.
The probable civs would be a no surprise inclusion in the game. The dev team might decide to throw a curve ball replacing India with the Mughals (alternative land representation) or Aztec might be replaced by Maya for the base game and released shortly later.
That leaves 3 i think left over which make more sense speculating about, with at least one most probably from the Americas (Sioux, Iroqouis etc.), one probably being African (Mali would be appreciated) and one being SE Asian possibly (Khmer or Siam or along those lines). Ed Beach (who is doing a good service for Civ imho) mentioned that one civ will be one not released in previous iterations, and an educated guess would be that it's the Sioux or Comanche (though technically they've been released in Colonization) or Ghana, Benin, Axum, Mossi etc.?
Regardless, as usual id like to see Armenia in the game they would have some cool abilities, or the Indus Valley Civilization one of the earliest civs, though their undeciphered language wouldn't help.
Sioux were in Civ II, and the Comanche received some representation with the Shoshone's UU in Civ V. Armenia though, I would love to see them in the game. Really an interesting culture.
Another Civ I think would be a great addition to the game, and represent Sub-Saharan Africa, is the Kingdom of Dahomey, led by Agaja. His trade for weaponry, as well as his real life Amazon soldiers, would lead to some unique options as a Civ.
EDIT: I probably misread, and you were referring to the Comanche being in Colonization.