Housemarque has announced Returnal: Ascension which is a 3.00 free update releasing on March 22nd that adds quite a bit of functionality to the game.
The update will add an online co-op mode that will allow you to play through the entire campaign with another player.
It will also add The Tower of Sisyphis which is a horde mode that will add increasingly dangerous phases, each containing 20 floors. Obviously, it’s going to be quite tough, but a great challenge for those that were able to finish the game.