You're really stretching your imagination. All the info from our MEC and the new DAL management team totally disagrees with what you just posted. After DCC, you'll start to see the DC-9 in ATL replacing 50's. This was stated by both our MEC and management.
You may not see 50's in the desert, but you will see a reduction in their flying(hence "equivalent"). DAL seems to be developing a good plan that does not include 50 seaters. It DOES include the -40 and -50 DC-9's(for the next few years). DAL also likes the A330. They DO NOT like the 787, so we will see what happens with the orders. New 737-700 (first one just delivered) and new 777 will both be a big player. You will also start to see 747-400 in ATL and 767 in DTW and MSP(that synergy thing...).
The above was stated by both DAL and our MEC's. This may change but it looks like the direction things are moving. RA is a sharp guy, looks like we are all giving him a chance. "Trust but verify".