While I would like a co-op mode for the game, I don't think it'll happen, simply because the dev doesn't think it's even possible to do, or might take too long to develop at this point.
I'm not saying it's set in stone, but the game is designed to be a solo experience, and I feel like it might be for the best, tbh. While I would love a co-op mode, you gotta admit that having someone else there with you would probably make the game a lot less spooky. Most of the spooks COME from being alone during everything that can happen in the game.