Originally Posted by MysticRain
I would think they have to kill one of them in Avengers 2. Or at least make them disappear.
Iron Man - too cool to kill
Hulk - becoming popular, safe for now
Thor - every movie needs a comic relief
Cap - of the main four, he is the most vulnerable. Already mentioned, he has a suitable replacement.
Black Widow - the only female superhero, so safe
Hawkeye - likely to die
Nick Fury - very likely to die
Maria Hill - her death wouldn't really matter much
Also, I think the decision will also come down to the actors. Yeah, many are still under contract, but I can see if someone starts frequently expressing snarky/ill comments (maybe they've gotten too big or just bored with the role) it might factor into the decision of getting rid of that character.
She could easily be killed off or turned villain for a while and be replaced with any number of other great female superheros.