Think of programming like science (hence computer science).
Just because there's thousands of years worth of research in a given area (rocks, enviroment, human anatomy, etc)
all of that research is used to better the scientist.
Now look at computers, which are rapidly growing and expanding. You may say we're close to the pinnacle of computers, I mean look how far computers have come in the past 20 years when computers like the altair were run off of BASIC.
But!!! We're not even close to the pinnacle of computers. Take something like AI, AI was originally thought to be invented sometime early in this century. But real AI is still probably thousands of years away.
So until there's fly cars, robotics pet animals, talking trees, and Mechanical women, there's always going to be a need for programmers.