This is also why Gardians of the Galaxy has a decent chance of being made as well since they are the Avengers of the Future. However, all of this is dependet on how good they pull off the Avengers, and how the audiance respondes to it. Honestly if Marvel still had the rights to Spiderman they would be doing him instead to integrate the dopey-rebellious-overdramatic-teens into Avengers but they don't so it's mute. The drop in performance in Superhero movies has more to do with how Hollywood normally approches movies in general. You can see this trend if you graph the original 4 superman movies and it forms a nearly perfect trend where it looses nearly 10% of it's max value each year. The original 5 planet of the apes movies follow an even steeper trend losing 15% each year with the final movie showing they had lost eveything exept the core audiance. However if you take something like Potter it goes though a predictable loss with each of the first 3 moves but then it stabalies and then Spikes at the final movie. And Lord of the Rights shows a linear increase gaining 8% each year. The difference between these is the Standard Hollywood approche to a franchise vs somone who wrote out an overall plot and Hollywood is just happeing to follow that plot. The primary risk right now is Over Saturation of the market where bad hollywood super hero movies a la X-Men Spiderman Fantastic Four and all of DC (Superman and Green Lantern) vs Marvel trying to do things differently with the Avengers franchise.