It seems no airline can justify the whales. They are being retired as fast as airlines can park them. Keep in mind that Delta's 747-400's are among the very oldest flying. NW was the launch customer if I recall correctly.
I doubt this will happen but there might be a glimmer of hope. The jets being parked are leased. Perhaps were playing hardball on the lease rates. The value of the jets is scrap value only. The owners at best can part them out. Since Delta has not displaced pilots perhaps it's a ploy for lower lease rates. Still no one seems to want them worldwide and the economic numbers for parking them were compelling when given to the union.