I had a delta guy on the JS. He just upgraded to the 737 in LAX. 17 yrs on property. He said he could hold right seat 777 LAX and he'd be 2nd from the bottom.
I'm sure he could have upgraded sooner but I didnt get the impression very much sooner.
Either way there's always the grass is greener stories at every airline. I'm glad now people have somewhat of a choice compared to 10 years ago.