Pax East had a Firaxis Panel
that discussed Civ5 and XCOM (starts about 5 hours, 20 minutes in). They also talked about the development process quite a bit. They planned to include a Pueblo civilization that represented both the Pueblos as we know them and the earlier Anasazi cliff dwellers led by Popé. Unfortunately, they had to leave them out when Pueblos objected to one of their most revered leaders being represented in a video game.
The game demo starts at about 6:03 or so
However, for substantive information:
You get to see more Poland
Assyria confirmed in (Ashurbanipal as the leader)
Brazil is in
They discuss trade Caravans in considerable more detail
And, for fun:
[spoiler=Right at the End]They reveal a new future unit: XCOM Squad, that acts as an advance paratrooper and can have their Skyranger drop them 40 tiles away to respond essentially anywhere in the world when needed).