A member of the Croteam game studio revealed that a new Serious Sam game was on its way, along with a new IP and, if history is any indication, both of them will be available for the Linux players also.The Croteam developers made a name for themselves with these insane games in the Serious Sam universe. The latest one that they made, Serious Sam 3, was ported to the Linux platform and for a while it was the flagship title on Steam for Linux.
Serios Sam 3 was the first major title available on Steam for Linux and remained the best-looking game on the platform for many months. The developers also made a lot of improvements to the engine and to the game in order to make it run flawlessly on the open source platform.
The announcement regarding Serious Sam 4 and the new IP from Croteam was published by a member of the studio, Alen Ladavac, who is also Linux fan. There is no mention of a Linux version, but we can safely assume, given the rise of Steam for Linux in the past year, that the game will be launched on multiple platforms simultaneously.
Besides the release date of Serious Sam 4, in Q4 2014 (this might mean the end of 2014 or March 2015), there aren't any details available. On the other hand, the new IP will be an FPS and it has been described as a mix between Portal and The Witness.
Well keep you apprised with any new details about these two games, as they become available.