Given how successful Guerrilla Games’ Horizon Zero Dawn turned out to be, it’s not surprising that a sequel, we’ll call Horizon Zero Dawn 2, is being edveloped. What’s surprising is, a new rumor has surfaced stating that Horizon Zero Dawn 2 will feature some kind of co-op, and is being planned as a trilogy!
This rumor was posted by VideoGameChronicle, which mentioned that development on the sequel started after the first one was released back in 2017. In another not-so-surprising bit of info, the rumor also mentions that development has shifted from the PS4 to the PS5, which is understandable, given we’re about to usher in the next-gen of gaming in just a few months’ time.
Allegedly, a standalone co-op game preview (demo?) with progress carrying over to the full version of Horizon Zero Dawn 2. The sequel is also said to be “gigantic” in scope, with a larger game world and give players more freedom to explore compared to the game first. It’s worth noting it’s not known at this time whether the rumored co-op feature is part of the main campaign or a separate mode.
Note that this isn’t the first time Guerrilla thought of including a co-op feature in the franchise, as Horizon Zero Dawn’s concept art (which is pictured below) even shows multiple players battling a dino mech.

Bear in mind that none of the info is true, but if it is, I wouldn’t be surprised as adding multiplayer component to the franchise would certainly be a good step forward for those who want to take down mechanical monsters with buddies.
If you don’t have a PS4 or have yet to play it, Horizon Zero Dawn is headed to PC this summer barring any unforeseen delays.