As far as I know, Xbox Live servers function on Microsoft's Azure platform? They'd have excellent economies of scale with this.
I am sure there is *some* maintenance needed to keep each individual game up and running (once the initial updating/DLC process is over), but by and large the resources for the servers themselves would be decided by the total number of people on Xbox Live to play *any* game.
As such, I view it as highly unlikely the servers would go off until some time after a major new iteration of the franchise released.
As they haven't said the game is online only, I also fully expect to be able to play the full single-player offline, but it would be nice if the physics were enhanced if I play online!
starcraft - Playing Games = FUN, Talking about Games = SERIOUS
