Depends on what they’re going to do. They can do a hybrid system like Warframe, where you have servers which can help link players up but once they’re off on a mission it becomes strictly P2P.
With how large the procedural universe is, I don’t think there’d be a need for a server-based MMO setup where everyone is playing “on the server”, but who knows. I think we’ll have a better idea once we know what it is they’re wanting to do.