Despite my sadness that S.T.A.L.K.E.R. 2 may never happen, Vostok Games' MMOFPS Survarium might just fill that void. In a blog post today, the developers outlined the timeline they are aiming for and when players can get early access to the game.
Vostok plans to have an invite-only alpha sometime in Q2 2013, with a beta version in Q4 that will likely be open to all. Players invited to the alpha build will initially be testing hardware issues like server stability along with PVP areas and in-game tasks.
Considering Vostok is staffed by many ex-S.T.A.L.K.E.R. devs and that early screenshots show a ruined central European location, it seems that Survarium will be treading a similar path. Adding online co-op and multiplayer would be something I'd love to see added to that style of game.