First released in 1968, Boeing’s 747 was, and still is, an engineering marvel.
United is retiring their 747 fleet for more fuel efficient 777 & 787 aircraft and fuel efficiency is a definately valid reason. Other airlines will continue to fly them so the iconic look will still be seen in larger international ports. However their numbers may continue to dwindle as technology changes.
I’ve only flown the 747 six times in all of my travels on these routes: Miami to Aruba, San Diego to London, Los Angeles to Sydney. Thus far it is my favorite airliner. The adjectives roomy and majestic come to mind. I even know the layout well enough that I have a favorite seat. I’ll miss this mighty bird for she gave me many wonderful memories.
Fearsome Beard 
Did you see that they are taking bids of frequent flyer miles to be the first to board the last flight?
have never flown in a 747; DC-10, L-1011, 707, 727, 757.