The fate of Doctor Brenner has been disputed among fans, but the Duffer Brothers have "confirmed" that he is not dead! (note the quotes :P)

This is what Matt said:
"I would say that if we were going to kill Brenner… as an audience member watching the show, if that was his death, that would be very unsatisfying to me – when the monster jumps on him and we cut away. He would deserve much more than that as an ending. So yes, there’s a possibility of seeing him again."

What do you think?