To be honest, I'd like to see what Paradox could do with Civilization anyway. It couldn't be worse than Civ 5 Maybe if we can convince them to buy the IP rights to Call to Power...
I don't know, I can't go back to Civ 4 after Civ 5. Even then Civ 3 was my favourite, and I can't go back to that. And the new expansion is rather good.....actually, not rather, VERY good.