I'm just now realising that if Agent Coulson does not turn up at the start of Avengers 2, with a 'haha! fooled you! SHIELD agents don't *die*', I'm going to spend the first 20 minutes of the film crying over my lost hope. I love Agent Hill, I do. But... no.
One of the interim films would also be acceptable. Especially if it's the Black Widow and Hawkeye film.