yes, they could kill either Spock or Uhura and I definitely take this idea into consideration. Mostly because they said that the sequel is "bolder". (though, if Uhura gets pregnant.. now that's bold for a whole list of reasons!) But at the same time, it wouldn't make sense for them to kill one of the main characters NOW, in a reboot that is just the beginning of the story and after the writers had talked so much about them making the characters the crew that we know and the sequel being the movie that made them a true group. Killing one of the main tos characters is a huge risk because it wouldn't mean just killing them in this movie, it would mean getting rid of them from the whole current star trek franchise and possible future movies, tv-series (animated), comics, novels etc etc.. though, to be fair, people died and resurrected in the prime universe so even if they kill off one of the characters chances are that they can always find a way to bring him/her back.