When he's right he's right. The superhero film genre is a bubble getting ready to burst but it's not the first time Hollywood exploited a genre for guaranteed money until it killed it. What immediately comes to mine are the Westerns and WWII movies that dominated the "John Wayne" era of movie making. It was very similar because among these guaranteed money makers you had the same output of book adaptations and a small amount of critical darlings.
It's also not the first time the bubble burst on superhero movies. From the near stillbirth of the genre by the, criminally underrated, in my opinion, Howard the Duck to the coma that Batman and Robin put the genre in to. There have been a number of stumbling blocks for comic adaptations in the past and this seems to be the golden age they finally deserve. The stories are being taken seriously and being given the time, effort and money they need to flourish. The movies are no longer dismissed as "Only a comic book." which is something Joel Schumacher said in defense of Batman and Robin. But it will pass, people will get sick of it and the easy money will dry up and the big IP's with it. Ah well, hopefully we'll get to see some more great things before that happens.
Here's what I want to see before the genre dies (or at least goes back into a coma):
-An Avengers movie with Fal-cap and Lady Thor.
-The Marvel Netflix TV verse ending up with a made for Netflix movie of New Avengers (sans Spider-Man and Wolverine of course)
-Spider-Man: Maximum Carnage
-Avengers cameo on Agents of SHIELD
-Mongul in a Superman movie
-The JLA movie
-An Aquaman movie
-A Howard the Duck remake
-Armless Tiger-Man in a Cap movie
-The Question on Arrow
-Flashpoint on Flash
-Flash's Rouges being bro's like they are in the comics
-Joker on Gotham
Keep in mind that when the bubble bursts we probably won't see the last of the superhero genre. Unlike westerns or even WWII films the superhero genre taps into something primal, something basic, and provides that fantastic escapism and wish fulfillment in a way that few genre's can. Christopher Nolan's Batman Begins was sort of like the superhero genre equivalent to Unforgiven which made it "okay" to like and make westerns again after a pretty long hiatus and it just came back stronger than ever whereas the western is still in short supply. What will likely happen is the current Marvel "Phase 2" and DC's "Movie Clusterfuck" will run it's course, making less money as it goes and "Phase 3" along with DC's "Movie Clusterfuck 2: Clustershart" will be put on ice until they can make that next comeback masterpiece that will make everyone pay attention again.