S.T.A.L.K.E.R. 2 may have been cancelled, but it seems from survival MMOFPS, Survarium, will definitely suffice. Considering Survarium is from the same developers, Vostok Games, and the fact that it's destined to be a free-to-play, massively multiplayer first-person shooter that's all about, er, surviving, it should be the goods.
Of course, it all takes place in a post-apocalyptic environment (what else, it is 2012 after all), the developers have teased the world with a bunch of screenshots, and a developer's diary video talking about the game. The video goes for a nice eight minutes, but unfortunately doesn't feature any in-game footage.
So, what is Survarium, what do you do? Well, players in the game have to complete missions for different factions in order to earn money and status, pretty much how S.T.A.L.K.E.R. was played. Players can also work together for co-op missions, form teams for player-versus-player action, or play in "free play mode", where they'll be able to enjoy the freedom of interacting with human counterparts in the game. RPG elements will also be at play, such as leveling up and skill specialization.
More screenshots available here.