The elephant in the room has been tackled right up front at the PAX East panel happening right now. Firaxis' Will Miller, who is co-lead designer on the Beyond Earth project, said, "The heart and soul [of Alpha Centauri] lives at Firaxis. For all the fans of Alpha Centauri, this is the game we've made for you."
"The biggest systematic change for Civ 5 is that tech is a web, not a tree," said David McDonough, the other co-lead on the project. "By the end of the game you've got 70 percent of the web." He notes this leads to two cultures having radically different techs, where genetically modified aliens can fight sentient robots.
Beyond Earth will have players assembling their cultural identity and craft their colony before exploring their new world. The game will also add a quest system (something very new to the series,) for players to learn more about their new planet. We've got more details here. The game is set to land this fall.
Civilization: Beyond Earth (4/12/14)