The first 'Saturday Night Live' season I was heavily interested in was the one with Martin Short, Billy Crystal, and Christopher Guest. There was just something about Martin Short in particular. I really related to him and hung on his every word and mannerism, so I started impersonating all of his characters as an 8th grader.
There is no more reason to think that they expected the world to remain static than there is to think that any of us holds a crystal ball. The only way to create a foundational document that could stand the test of time was to build in enough flexibility that later generations would be able to adapt it to their own needs and uses.