Yes, Dead Island 2 is playable across both Xbox generations, meaning Xbox Series X|S and Xbox One players can share the same lobbies (just like PS4 and PS5 players).
However, due to a "known issue" with the game right now, Xbox One players cannot host Xbox Series X|S players in Dead Island 2. The developer is aiming to address this with a post-launch patch coming "early summer", but for now, this method won't work.
So, to play Dead Island 2 cross-generation at launch, an Xbox Series X|S player must host the online lobby. If you need a little assistance in getting started with Dead Island 2 co-op, check out our handy guide down below.
We hope this helps with your Dead Island 2 crossplay experience on Xbox!