Jumbo jets are not being retired. That term applies to any airplane with two aisles between the seats or a "wide body". Currently produced examples from Boeing are the 767, 777 and 787. The 747 is simply not economical when compared to those newer airframes. Mot of the final run of 747s and I believe of those still in operation are used for cargo operations, this was an expected outcome even in the 1960s, although for different reasons. For airlines it is about running the plane at capacity and minimizing time on the ground. Airlines choose specialized models for the routes they run. The super jumbos are simply too big to be practical or economical.