Carl,
You really need to start understanding the mindset of the Delta bureaucracy. Regardless of the fact that RA was former NW and half the senior executive suite is former NW, the management minions, much like the eunuchs of the old Chinese Emperors, are the true decision makers.

The ATL airport is incapable of handling the A380, and there are no plans to ever modify the infastructure to do so. Accordingly, DL will not operate the A380 because, even though LAX and JFK can handle it, ATL can't and therefore DL's eunuchs, not being able to see beyond the borders of their fiefdoms, will determine that we don't need it.