Obsolete
B747 obsolete... Depending how you you look at this thing.
Looking at the financial point of view I am sure that Classics will be very uneconimical to operate compared to newer types of the same size. This does depend on what kind of flying and what part of the world you intend to fly the ole Jumbo. Lower purchase price of an old airplane can more than offset the higher fuelburn, three pilot crews and higher maintenance costs. Ie there will be a market in some parts of the world for the classic for quite a while, 20 years, your guess is as good as mine.
The newer -400 will probably be soldier on for another 30 to 40 years and new version coughed up.
Just have a look how long the B707 and B727 have been around. Both have been out of production close to 20 years.Mods are still being designed for both airframes to keep them running.
As for Pilots becoming obsolete. I do not think so. Would you fly in an aircraft without crew? I would not.