I think you should do it on general principle.
On topic... I've heard people thinking that it's either Agent Coulson (because of Whedon's love of killing fan favorites and the recent extra stuff he's been doing) or Hawkeye (the lack of any dialogue in the trailers isn't a good sign).
I would be very surprised if its Hawkeye but I wouldn't bat my eye over Coulson as I have no attachment to him whatsoever. It would make sense if its Maria as she is barely mentioned in the movie so her relevance wouldn't be played upon, making it easy to kill her off.