At this point, I just don't see how they could kill off Cap without it coming off as an attempt to be retro-actively shocking. Plus, it wouldn't fit the shape of the story, and Marvel is actually pretty decent about story-shapes.

And Quesada has actually explicitly mentioned that there was going to be one major death at the end of Civil War - someone who all of the superheroes liked and respected. And sad as it makes me, I'm almost positive that that's Aunt May. Particularly since I swear they were hinting that it wouldn't actually be a superhero who died at least a month or two ago.

Now if this were D.C., I'd be worrying too, but then Marvel's stupid decisions tend to involve more Ninjas than D.C.'s.