id Software has announced the next Wolfenstein game on their main page here. They have not announced its title, however it is being co-developed with Raven Software and will be available for both Xbox 360 and PC.
Once again it's based in World War II, but knowing the Wolfenstein series, there'll be Nazi zombies, mutants, or other fun occult stuff to deal with. A rather fantastical look at one of humanity's greatest conflicts.
Check out the web site for the previous Wolfenstein game, Return to Castle Wolfenstein, to see what I mean.