Months ago there was talk about a new S.T.A.L.K.E.R. game on the way. They got the title wrong, referring to it as S.T.A.L.K.E.R. 3, but nevertheless, there are in fact two new S.T.A.L.K.E.R. games on the way. One of them is a stand-alone expansion, similar to Clear Sky, called S.T.A.L.K.E.R.: Call of Pripyat, and the other is a true sequel to Shadow of Chernobyl named S.T.A.L.K.E.R. 2. Call of Pripyat is due out later this year, and the sequel will probably be out in 2010 or 11 at least.
http://www.shacknews.com/onearticle.x/58116