Re: Who dies?
It's probably Hawkeye. He has the most useless skillset of any Avenger and he'll never get his own solo film. I'd bank on a Black Widow or War Machine film before Hawkeye gets one. Joss is probably going to flesh him out, make him likable and then get him killed by Ultron which will resolve the love triangle with Cap and Black Widow.
Like I can't imagine an Avengers film without Iron Man and Captain America. Thor probably won't die until a Ragnarok film comes, Black Widow dying will piss off all the female fans and kids love Hulk too much for him to perish. That leaves Hawkeye with the noose around his neck.