I expect SSR to have it's own bus transportation to the resorts. To my knowkedge DIsney has not made any announcement about how it will be handled after the resort opens, but the resort will be large enough by itself to combine with another resort, IMO.
Some have reported that the boat to DD will be shared with OKW- a reasonable move since the SSR marina sits bewteen OKW and DD. It will add about 5 minutes to each leg of the trip. ( I also feel that the SSR marina is out of the way for most SSR guests to get to DD- walking will be much faster in most cases and not much further.)
Stay Tuned!