I don't see Delta keeping the DC-9 or the B-747. Delta is filling their fleet with Embraer and Canadair regional jets to replace their MD-88 and MD-90 fleet. The DC-9 will join the other two airframes that are slated for extinction.
Boeing's 747, while being one of the most beautiful aircraft ever made, is a dinosaur by modern standards. Four engines, three flight deck members, and a thirst for fuel has kept it out of Delta's fleet for over 30 years. Delta used the B-747 for a short period but they proved too costly to operate. The 777 is their long distance hauler and they are going to be eyeing Airbus for several of their products in the near future.
I see a fleet of Embraer, Canadair, B-737, B-767, B-777, and possibly the A-319/320 to fill out the hangar.