It seems that developer GSC Games is planning to release another standalone expansion to S.T.A.L.K.E.R. as well as an entire sequel to the game. The launch of S.T.A.L.K.E.R. was repeatedly delayed with the game finally being released for the PC in March of 2007. The first expansion to the game was S.T.A.L.K.E.R. Clear Sky released in September of 2008.
The expansion is to be named S.T.A.L.K.E.R. Call of Pripyat and is set for a fall release. No details have been provided on the new game but it has been confirmed to be in development by GSC president Sergey Grigorovitch.
S.T.A.L.K.E.R. is a first person shooter game based in an alternate reality where the Chernobyl Nuclear Power Plant sees a second nuclear disaster. As a result of this disaster, the area surrounding the plant has been changed and is now populated by strange flora and fauna. Even the laws of physics in the surrounding area have been altered. S.T.A.L.K.E.R. stands for Scavenger, Trespasser, Adventurer, Loner, Killer, Explorer, Robber.