Probably Justinian will become another possible leader for the Greeks. Makes the most sense, the map is otherwise just too small.
We'll definitely see the South East Asian civ in (given that they are included in bts). The rest is rather up for grabs. The Native Americans will probably not get in, as Rhye so far has stated that he would like to see the barren landscape of NA open for American colonization (and not conquest). That makes much sense to me, perhaps with an overhaul of diplomatics, Sitting Bull, Brennus and Shaka could pop up as Independents/Barbarians. I hope the Maya get in, although the map might be too small there. Nevertheless, a duel Maya-Aztec would be cool and would the Aztecs give an opportunity to use their uu.
Portugal and Netherlands are a though choice as they might be included a) with an enlarged Europe - don't think so, b) as one-city-in-europe-civs or c) as colonial late-starter Empires only (Portugal with Capital Rio, The Dutch with Batavia or CapeTown). Babylon is given, Sumeria out (Gilgamesh second leader for B?). If the map is remade to add more comfort here and there (it is a BIG project after all, not an update to BTS), we'll maybe see Maya, the Europeans AND Korea in which I would think would deserve a spot (although at the moment, Beijing and Japan are choking them).
That's just for the civs, I think we will see all kinds of other cool features again.
mick
EDIT: Oh, btw. just forgot to add that I am really happy and excited by this new, might be apparent though