Originally Posted by Lorus
I've never understood the mentality which would judge a character's presence on a team based on something like power levels. As soon as you do, you have to start drawing arbitrary lines in the sand as to what makes who worthwhile. If the team has Thor, it really doesn't need Iron Man, Cap, Black Widow or Hawkeye because he can do more damage and is more powerful than all of them combined. The point is that these characters are people, individuals who contribute more than just a power set. The whole point is that the team is more than the sum of its parts, so the sum of the parts aren't relevant.
On a side note, I think that given that Iron Man 3 is the last film RDJ is contracted for, it could be pretty powerful to kill him in an Avengers sequel and never risk over saturating an audience on RDJ's Iron Man. That said, I'd be perfectly happy with no deaths.
This is basically what I was getting at, but just stated far more eloquently.
I also agree with Chewy - any of these characters are really fair game to die by the end of the hypothetical third movie - and I trust Joss to, even if he's killing someone off, do the characters justice.
I think that, if Tony Stark were to die in these movies, it would happen in the third or possibly at the end of the second. It would serve as the most poignant and surprising (at least to the general audiences) death, seeing as he is the character most people have come to know best and serves as the comic relief.