The prequal to the heroically buggy yet innovative free roaming FPS S.T.A.L.K.E.R has now been dated; a worldwide release is planned for the 29th of August 2008. If you lived in a cave when the original was released, the basic premise of the game involved venturing into the Chenobyl nuclear disaster zone and trying to sort out the rather bad situation that is occuring there. The prequal follows the same sort of thing, but obviously will explain the back story to how the problem occured.

Via Press Release (private)