Joystiq have posted a brilliant article which includes a youtube video of STALKER 2 engine footage - personally wouldn't call it a gameplay video... since it's really just exploring the environment beautiful landscape.
Also while some people would be aware that there is a STALKER MMO in development (I personally had no clue!) the beta is open for anyone to play. Check the Joystiq link.
Edit: I should add the beta is only in Russian