Well, you probably haven't been paying much attention to the latest news. Civilization Resolution is a game built specifically for next-gen console, that meaning that it will NOT be a sequel to Civ IV. That said, this version is a lot lighter than its PC "cousins", and designed to easily be played with console controllers, therefore losing a lot of the depth (presumably) available in the other versions. It's Civ adapted to the more mainstream reality of consoles.
Pc players, however, have not been forgotten. Civ V won't take long to start its conceptual design (IMHO), and will probably released in the next three years. Meanwhile, it is very likely that we either see another remake of one of Sid's classics (just as we've witnessed with the new Pirates!, or the more recent Railroads!), or another game made by Firaxis for the PC, built from the ground up.