Oblivion Lost has a post from Andrew Prokhorov, Lead Designer on S.T.A.L.K.E.R.: Shadow of Chernobyl talking about the game's current status.

No new release dates are mentioned though. Sometime in Spring 2006 was the last I heard.

Once key areas were identified we were able to work on filling out the content of the game world and being the process of polishing and balancing. At the same time, we are working hard to refine the AI, life simulation, the PDA interactivity, bug fixing and optimising the game to run on lower-spec machines. The 'eye candy' is also getting a major overhaul…