They can in theory live together, but like...just not with the current crop of humans. You have to be exposed early to the Dark Ones powers as a child to survive them as an adult. There are also certainly other tribes of Dark Ones out there. Novosibirsk has a few of them around the place, and there's the theory that the mutants that you can hear the thoughts of, are actually just the Dark Ones sharing the thoughts with you.
In the Long Term, you can probably live with them in the sense of sharing a planet, but like...the Dark Ones thrive in death field levels of radiation, and kill humans if they think at them too hard. You can't share space with them.
Anyway, calling it now: The main villain is you in the new game. They will use the Dark Ones to brainwash people, and you got mind wiped and woke up because of a dark one. That will be the twist. My $100 bet is on the table. Also, I can read roosky; and I read some of the other novels; they are truly dogshit bad lmao. Fallout tier material, completely undercuts the tone of the main series. You've got crab men, psychic humans, fish people, etc. Don't read them, they ruin the tone of the series completely. It sucks away all the uniqueness.