From an interview Bitmob conducted with Civilization 5 Lead Designer Jon Shafer: 'You can import Civ 4 maps into the world builder and convert them into Civ 5 maps, including all the units and cities and stuff on it — the conversion process will just do that for you automatically. We're hoping that the first week Civ 5 is out, people will use that function and port all of the Civ 4 stuff over to Civ 5, so everything will be out there already.

http://games.slashdot.org/story/10/0...ert-Civ-4-Maps