Independent Croatian developer Croteam officially announced Serious Sam 4: Planet Badass. A teaser trailer showcases the game's improved visuals. The full reveal will take place during Devolver Digital's E3 2018 conference in June.
Featuring the world-renowned signature Serious Sam gameplay on a brutally bigger scale, and not a single desert level, Planet Badass will make its debut @ E3 2018.
Not much is known about Serious Sam 4, but the trailer and its brief description seem to suggest that the game will feature much larger environments than previous entries in the franchise. The last main installment, Serious Sam 3: BFE, launched in 2011.
There's also hope for a better screenplay, given that Jonas Kyratzes (one of the writers behind the acclaimed The Talos Principle) is working on Serious Sam 4.
The Steam page also lists local co-op, split-screen, cross-platform multiplayer, a level editor and Steam Workshop support as features. There's no word yet on a console release but looking at the history of the franchise, it seems likely that it will happen at some point.