fans will move on from iron man and cap if we get x-men + fantastic four, spidey keeps killing it, and they continue to deliver epic storytelling that leads up to another cosmic-level threat via kang. the individual iron man and cap IPs might suffer, but iron man and cap have never really been on the level of spidey and wolverine. it's why you saw spidey and wolverine join the avengers when marvel re-prioritized the comic title. it's also why marvel has never been able to fully duplicate iron man's film success in the comics.