Oh, I think Disney would allow it in a heartbeat if S/D ante'd up sufficient cash. They could always put them on the same buses as BW & YC.
Having said that, I really don't think that S/D will feel any need to make that investment unless their occupancy rates fall drastically. Right now that isn't happening, and their convention bookings are doing very well, so I don't think it will happen in the foreseeable future.