Delta needs the W/O for flexibility. They can increase and decrease the flying as they wish. You will never get that kind of flexibility with a contract carrier. Even if Delta wants to sell the W/O, they will have a very tough time finding a buyer. The days of guaranteed fee for departure are long gone. The contract carriers will have to share the risk with major carrier on any new contracts to be signed. Sharing expenses and risk is not a good thing for contract carriers. IMHO, you will see a couple of W/O and 2 contract carriers flying for DCI.