The 717's are not DC9 replacements, they are CRJ-200 replacements, ie:they are growth aircraft.
The 35 MD90's we are receiving over the next 2 years are the DC9 replacements.
The 100 737-900ER's we are taking delivery of over the next three years are replacements for the oldest 757's, 320's and the domestic 767's.
There may be a lawsuit or two initiated by Air Tran pilots who would like to come with the aircraft. That's to be expected. But, our SVP of Flight Ops has publicly stated and without equivocation that these aircraft would not come with pilots.
Further, the 717's are being leased to Delta directly from Boeing.