Helldivers 2's developer is potentially open to collaborations with others games, but it would be very dependent on which games.
A Helldivers 2 player recently asked developer Arrowhead about potential future collaborations in the game's official Discord channel. Community manager Twinbeard says that while Arrowhead looks at potential crossovers with "interest," it also needs to be very mindful of the game's "fantasy and lore."
"As a couple of examples: Melee weapons could be plausible in Helldivers. Lightsabers from [Star Wars] would not," the Arrowhead community manager explains. "A helldiver finding a remnant, artifact, or a letter from someone from another game/cultural universe is plausible. Mickey Mouse writing a helldiver would not. And so on.
The Fortnite and Kingdom Hearts comparisons are pretty telling about Arrowhead's mindset. Both games have become synonymous over the years for bringing together characters from all over the world, in wildly different franchises, to play together or opposite one another, and it's pretty clear that Helldivers 2's dev doesn't want it to lose its own identity.
Other developers have even been asking for a collaboration with Arrowhead in the wake of Helldivers 2's smash-hit success. Deep Rock Galactic players were drawing favorable comparisons to Helldivers 2, and while the developers of the former game quashed any competition between the two titles, Deep Rock Galactic's developers did ask Arrowhead to "please hit us back" for a team-up.
