S.T.A.L.K.E.R. 2 has had a tumultuous development cycle, previously being announced and then later cancelled in 2011. The announcement also leads to a new website that shows the date 2021.
There's bugger all info available at the moment, but fans of S.T.A.L.K.E.R. can rejoice: you're getting a sequel. The bad news is that it's not going to happen anytime soon: The Stalker 2 site now indicates that it'll be out in 2021.
"Today 15.05.2018. I officially declare: GSC GAME WORLD DEVELOPS S.T.A.L.K.E.R. 2", reads Grygorovych's post, followed by a link to the promotional website for the game. As for what the unusual acronym means, it was apparently revealed to be "Scavengers, Trespassers, Adventurers, Loners, Killers, Explorers, and Robbers" back in 2012 when the first attempt at making S.T.A.L.K.E.R. 2 was underway.
As for the game engine, nothing has surfaced yet. The headquarters of GSC Game World in Kiev. Do you think S.T.A.L.K.E.R. 2 will be able to go head-to-head with similarly-themed franchises like Metro and Fallout? The game's site simply has a dark concrete background with "S.T.A.L.K.E.R. 2" and "18.104.22.168." painted into it, likely indicating that this game won't be around until another three years.