I think there were a couple of step-changes
(1) the arrival of the DC10/L1011/747
(2) replacement of the above with the MD11 & 747 BUT on many routes the replacement of the above with the 767 was for cargo retrograde
(3) I think it was the A340 that first made me start checking a lot of numbers when AC started transatlantic and averaging 20-23 tonnes westbound ex LHR & FRA
(4) the 777 family
Tha A380 is like the 747, good for pax but less of a cargo lifter, unless you have the Combi version (ah, but not yet fior the A380 and the 747-8i)