The following info is from a reliable source but isn't official, keep that in mind.
Sergey Grigorovich didn't sell the brand name "STALKER".
Bethesda is going to publish a STALKER game and has all the rights to it.
The game is multiplatform(consoles+PC) and is based on Bethesda technology.
It's being made by a studio familiar with that technology(possibly Obisidian or the Fallout 3 team from Bethesda, but no facts as of yet). It is almost 100% guaranteed that it's not a Ukrainian studio.
Bethesda will be able to buy the brand name from Grigorovich later, but for now all the misc. merchandise is his responsibility.
Release date, engine, detailes - TBA.