Well, it has been leaked that three secondary character death scenes were filmed. Only one is going to be used. I don't want to potentially spoil anyone, so google it if you're interested.

They filmed two character death scenes for AoU and only used one. One was for the final film, the other was for misdirection and fan speculation.

Also, it's been pointed out that in the trailer that Bucky mouths "Steve's dead" in the trailer, so I'm pretty sure they are going to kill Steve, but I don't really think anyone should be surprised by that if they know anything about the comics. Doing the Civil War storyline without killing Steve would be pointless.