Most times the meaning is not literal. No one will die. It is usually taken to mean "You will be in a lot of trouble" or "You will lose your job" Another slang phrase that means the same thing is "You're luncheon meat."

你死定了！

You will be dead (in the near future). meat: body Your body will be dead meat when I'm finished with you. (I never said that...) This is a threat to kill someone. Sounds like from an action movie.