I like the list so far. A little small, even more disappointing that Firaxis stiffed us with leaders, but the nations themselves are good picks. For an X-Pac I'd like to see
19.Mesopotamia(I think we need to represent Sumeria, Akkadia, Babylon and Assyria as one, for a world map's sake and because all the mesopotamian civs were important, but putting them all in seperately where they become world-spanning empires is excessive considering all the civ's we'd like in)
20.Ethiopia
21.Khymer
22.Portugal
23.Netherlands
24.Poland-Lithuania
25.Turks/Ottoman Empire
26.Iroquois
27.Scandinavia
28.Maya
29.Phonecians(Or Carthage. Theoretically they could cover each other if someone so desired, as they were both influential but highly related, as Carthage was once a colony of Phonecia)
30.Polynesians(hey, they really deserve a hats off. They had mastered the pacific while Europe believed the world to be flat. The evidence is that polynesians sailed not only to South America, but possibly even to California. They were expert colonists and had an extremely advanced navigation system, allowing them populate large areas of the Pacific. They were also fine stonemasons, leaving many enigmatic monuments across the pacific, most well known are the stone heads of Easter Island. Their society too was well organized, with a strong authority structure, based on geneological ranking, and strongly focused on overseas colonization. Plus the UU would be awesome - Voyaging Canoe, replaces Trireme, only 1 strength but can cross coast, sea and ocean, carries 1.)
But that's for the Xpac. For now, I'll just say that leaders aside, I'm rather pleased with the selection of civs.