Based on a job posting on their website, Guerrilla Games may be developing a new online game with social aspects.
Because Horizon Forbidden West will be released soon and has a release date, it is extremely improbable that this new job posting is linked to the game. Instead, they are most likely working on a different project with multiplayer integration from the start.
You can learn more about the job opening for a Senior Social Systems Designer on their website.
Guerrilla is looking for an experienced Senior Social Systems Designer with a passion for player communities and social features. Reporting to the Lead Game Designer, you will work within a core team of multiple designers focused on social systems and player engagements, and take charge to ensure quality feature delivery. Leveraging your background and experience in Systems Design, you will ideate, create and share innovative features to build, engage, and nurture player interactions and relationships.
Based on the criteria listed above, it is safe to conclude that this will be a co-op game. There looked to be an emphasis on multiplayer in one of the earliest concept images for Horizon Zero Dawn, but it never made it into the final release. The sequel will be released soon as well, although it will not feature multiplayer. This most likely gives the impression that they are working on a whole new game, either in the Horizon series or a new IP.
Naughty Dog and Sucker Punch have already experimented in multiplayer with Ghost of Tsushima and The Last of Us multiplayer spin-offs, so Guerrilla Games may be the next studio to join them.
