I remember playing the first Killing Floor with friends who bought me the title when it was on sale. A fun, heavy metal sci-fi horror shooter with a laissez faire attitude towards blood and guts. It was great.
Five years strong and a million+ copies later, Killing Floor 2 has been officially announced with this short teaser trailer short on gameplay, but with cool backstory giving hope that maybe the next title will be a more robust game than the already full game (thanks to extensive mod support).
No release date is set but I expect more details to trickle over the next couple of months. The title is being developed for PC and SteamOS.