The slides for the roadshow are on Delta net. Note however that 2020 and 3 years from now are about the same thing. SD was asked detailed questions about the 88 fleet at the roadshow I was at. The retrofit for both ADSB and GPS plus a better FMS has been finalized and funded. The only question was if they do the entire fleet or retire 30 of the oldest without the mods. That was dependant on finding replacement aircraft for the right price. He implied it would be used 737's or Airbus 320's unless a screaming new deal showed up. Talked about a narrow body bubble starting to happen when the NEO and max ramp up deliveries. Service life on the 88's is 40 years verses 30 for the Boeings and Airbuses. The C100 order is not tied to the 88 replacement.
Edit: 37 additional A321's announced. That is probably what will drive parking the 30 MD88's.