Robert Downey Jr has yet to sign the dotted line for 'Iron Man 4' and there is a big possibility that he never will. Why not? The short answer is that Robert Downey ages while comic book Stark does not.

In a revealing interview with Variety, the Iron Man star lent his support for teammate Chris Evans, who plays Captain America.

Variety talked with the outspoken, actor and singer. His answers are consistent with what he has been saying all along?

"V:Were you nervous when they offered "Iron Man" to you?
RDJ: Nervous? I was begging. I was absolutely certain it that would change my life.

V: There used to be a sense when you played a comicbook hero it could hurt your career.
RDJ: Christopher Reeve went on and did a bunch of other great movies, and his notoriety from the "Superman" franchise helped that, and nobody held it against him. But the other thing is, everybody knows Chris Reeve was a really good guy. A lot of it has to do with personality. Are you the type of person who incurs ill will?"

"Iron Man" served as an introduction for Robert Downey to a younger audience. Having his heyday in the 80s, not too many would recognize him from his 'Bratpack' days.

The interview continues:

"V:How many more of these Marvel movies do you think there can be?
RDJ: The smart money is you have to look at everybody's age. I'll put myself at the top of the list. Sooner or later, they've got to start over and get somebody young. I'm not there with them yet. It really is the closest thing to being a beloved contract player with a big old-timey studio that there is right now. When you really think about it at the end of the day, these films are entertainment largely driven by young folks. There is something very honorable about that. I run into kids wearing 'Captain America' masks. My kid believes that Captain America is real."

Downey becomes brutally frank, and this can be perceived as his unwritten, unofficial resignation. It is a real problem that studios can't ignore. Hugh Jackman as Wolverine is in the same dilemma.

"V:What's a downside of playing a superhero?
RDJ: It's kind of like having a really cool TV job. They are always hoping they don't get picked up for another season; or they are wondering if they're going to get picked up for another season; or they have done so many seasons, and they are already sick of doing the show, but the show is so big, it's working well for them. Any of those three things is better than calling your agent and saying, 'Hey, anything going on? It's pilot season.' 

V: You're starting on 'Avengers 2.'
RDJ: This one is a very ambitious sequel. If you read it, it's dense, it's smart. Joss [Whedon] is a really smart guy. My 2-year-old is crazy about Hawkeye, and I think Jeremy [Renner] has a lot to do with the plot. There's always so many plates to spin to get these things half-right, and I'm really excited about this one."

Despite his tone of depicting the role as tired and saturated, he respects Joss Whedon's genius, and all the praises for his co-stars.

He speaks for himself, and his role only. Superhero movies will live on. Marvel will live on and even Iron Man will live on-but they have to do it without Robert Downey Jr.