My response is a resounding no. The superhero film industry has really only just begun to be tapped. Along with this there are many different storylines and characters to provide production companies with countless ideas for superhero movies.
To make things easy I broke up my response into two groups. Group 1 is your mainstream superheroes and group 2 is your lesser known. The reason for this is there will be two very different strategies for future movies.
Group 1. Mainstream Heroes (Batman, Spider-Man, X-Men, Superman, Iron Man)
All of these either have or will have a movie coming out every year. These are the blockbusters that cash in regardless of what critics think. Now most people will say these have been done and cannot be counted on for future movies. I disagree.
The current fad for mainstream heroes is the origin and younger developmental years of the hero. This opens up the possibility for future movies to focus on storylines that explore the latter years of the hero.
Example. The next Spidey flick will be a reintroduction of Peter and his teenage years.
What is stopping them from creating another movie two years later focusing on an aging Spider-Man who has been fighting crime for years? I would love to see a story about a man fighting crime for 15 years with no end in sight and how that affects his pysche.
The same can be said with the current Batman trilogy, X-Men first class and the upcoming Superman. All of these films focused on the origin and younger years. The next installments can be set years ahead. With new villains and a whole different target audience.
Also each of these mainstream character's has tons of different villians which opens up the doors for different movies focusing on a whole different threat.
These movies will still receive high budgets in the 100+ million. Your mainstream heroes will cover budget regardless of what critics say.
Moving on to Group 2. The lesser known heroes. (Green Lantern is the best example)
These movies will now move to low budget, unknown directors/actors. Green Lantern proved that a less popular hero will not smash the box office regardless of the budget. We can all say at this time that Green Lantern was a failure and movie studios will not provide this sort of budget moving forward.
That does not mean they will not make movies based on lesser known heroes. It only means the budgets will be ALOT less and it will actually require the movie to be good in order to be successful.
This could be good for the CBM. Instead of movie studios throwing money at a movie, they will be forced to make a quality CBM in order for it to be successful.
Maybe that means we will see some amazing CBMs come out based on comics only the diehards know of.
To conclude I hardly think the CBM is dying. I actually think the opposite. There are so many possibilities with the mainstream heroes that will provide potential movies for years to come. And we may see a drop in budget for lesser known heroes but the movies will still be made and they may even be better when they can't rely on money to sell the movie.