I don't think there's a need to murder key characters. That's what irritates me about Marvel today. They kill people regularly only to bring them back just as often. There's nothing wrong with retirement, taking some time to teach young superheroes, or ruling the Shi'ar empire, or moving a character onto another team that doesn't get documented on screen. They already retired Iron Man in order to make room for other franchises. He's to continue in other franchises via cameo appearances and supporting roles. Ant-Man is coming! It's the first movie of "Phase 3". They also just signed up the director for the Dr. Strange movie.

Guardians of the Galaxy are mostly unknown so it will be interesting to see how that turns out.