The question of of where they might fail — besides audiences changing their tastes — is also interesting, and the article-writer comes down hard (but fairly) on diversity (hence the pic below).
Not that Blacks or Hispanics or Women (etc.) will only go see a super-hero flick that headlines someone who they identify with in that way, but good marketing would indicate that Marvel needs to do something there other than supporting characters (even good supporting characters). That's not pandering (quite), and it's not a call to have quotas — it's just a recognition of how to build and maintain a maximum audience.
Ironically, this points out how institutional bias can have an knock-on effect long after it's over. One reason Marvel is busy headlining movies about white guys is because in the early eras of comics (and later than that), that's what was the natural thing to do in any sort of comic book character. Captain America is a white guy because you didn't have successful Black or Hispanic (or Women) super-heroes in the 1930s-40s. Thor is white because we pay more cultural attention to the Norse mythos more than, say, the Zulu mythos because of where more of our population came from — and, again, that's what the white guys in the Bullpen were creating and writing and drawing back i the early 60s. Iron Man is white because that's what industrialists and inventors looked like in the early 60s. (And, presumably on all of these, because most comic books were bought by white kids.)
Those factors are different today, but diversity is still slow in coming to comics (and comics creators), let alone to the silver screen that is adopting their stories. That means that Marvel Studios (et al.) need to take some special steps if they want to break that mold and appeal to — and so maintain as customers — a broader audience.
Why Marvel Studios Succeeds (And How It Might Fail)
In six years and ten movies, Marvel Studios has avoided both critical and commercial disasters. How does Marvel do it, and can they keep doing it?
While I loathe to think of Robert Downey Jr. giving up the Iron Man role, I'm all for it being taken up by a handsome Asian dude.