Earlier this month Spielberg told the Associated Press superhero movies won’t last forever.

"I still feel that way. We were around when the Western died and there will be a time when the superhero movie goes the way of the Western. It doesn’t mean there won’t be another occasion where the Western comes back and the superhero movie someday returns"

​Batman v Superman: Dawn of Justice director Zack Snyder, to an extent, said the same thing but he isn’t worried about people getting sick of Batman and Superman, considering they’re both box office guarantees . 

​Marvel CEO Kevni Feige told IGN that if Marvel sticks to their routine, audiences will stick around.
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"In 2001, 2002, 2003 there were two Marvel movies, three Marvel movies, and I still believe the same thing, which is as long as the ones that we can control are as good as they can be, that’s all that I care about. I think we’ve been doing pretty well. I’m very confident in the films we’ve announced that we have coming forward that they’re going to be surprising and different and unique. I’ve said a lot: I don’t believe in the comic book genre. I don’t believe in the superhero genre. I believe that each of our films can be very different"

"It could, but the Western lasted 40-50 years, and they still pop up occasionally,” Feige said. “It’s been, what, eight years since Iron Man 1 if we count that, which I do, as the beginning of our MCU? Maybe [the superhero genre] will only last another 42 years."