An interview with Soren Johnson, lead designer for Civilization IV has been posted on Planet Civilization.

Can you tell me anything about Sid's next project?

Soren Johnson (Firaxis): We have a bunch of games in the making. We were just acquired by Take2, and that's opened up some extra resources for us. Sid has been open about the fact that he has been taking a look at the next generation of consoles. <snip> We're also looking into some older pieces of IP that Sid has, that people were fans of in the past and that we might re-develop in the future. We're also talking about some brand new original PC strategy games that are fresh. We're probably going to be developing a couple of these at the time. Should be an exciting time for Firaxis.