Up until 10 or 15 years ago, the commercially viable superhero film genre didn't even exist. Oh sure, we can talk about the Christopher Reeves Superman movies (at least the first two) and various Batman movies of differing quality, but beyond that, superhero movies really weren't a thing. There were also a couple of decent X-Men movies, followed by a lot more that frankly were terrible. Then Iron Man came along, followed by a whole slew of other Marvel movies. DC / Warner tried their hand at superhero world building (and largely failed, IMHO). The Incredibles was in there too, of course.
A lot of these movies have been critical in financial successes; several others have just been crap. But as a respected and lucrative film genre, it's been a very recent thing.
So no, the superhero movie genre won't last forever. But it'll be back eventually. Do you remember a film called Cutthroat Island? It starred Geena Davis, and it was a horrible flop. It basically killed the pirate movie genre for a lot of years. And then the Disney folks decided to make their Pirates of the Caribbean ride into a movie, and suddenly pirate movies were a thing again. The wheel turns.