It's unclear whether GSC Game World's sequel to S.T.A.L.K.E.R. will ever be released, but the news we've seen come out of the studio has been disheartening. But there is some good news — a number of ex-developers have formed a new company, with the intentional of creating a "cross-platform" title inspired by "Fallout, Mass Effect [and] Rage".
Called "UnionStudio", the company's LinkedIn page is currently the only source of information on its plans, so it's unclear whether it will try to build the game on its own, or seeking funding from a publisher. Per the LinkedIn description:
New company, created together with the best professionals that worked for GSC GAME WORLD and other AAA class studios.
We are developing cross-platform action shooter which will be available for PC, Mac, PlayStation, XBOX.
It has a kind of similar setting to such games as Fallout, Mass Effect, Rage.
Saying it's early days would be a monumental understatement. From the looks of things, the company is extremely new and I doubt any solid work has been done on its debut title. I wrote back in 2006 about the work THQ had to do to actually ship the original S.T.A.L.K.E.R., though I'm sure these guys are a lot more pragmatic about games development, especially after the troubles of GSC Gameworld.