Helldivers 2 did its first crossover event with Killzone, recently, and it didn't go too well. That's mostly because it was composed of weirdly expensive items that operated outside of the typical Warbonds system, leading to a community backlash so strong that Arrowhead released the second half for free by way of apology. The roller coaster ride continues.
Still, that's just a monetisation problem, and it'll be easily solved in future updates as Arrowhead experiments—and while the game doesn't want to become the Fortnite of grimdark futures or anything, there's one obvious crossover that'd be an intergalactic no brainer: Warhammer 40k.
