I've read a couple of interviews from Greg Nicotero, Scott Gimple, and Gale Ann Hurd and they all claim that we will find out who was killed in the premiere. I'm hoping we get it right away. Just like the opening scene of Season 6 Episode 7 when we find out Glen was alive.

Another interesting thing is apparently, only a handful of the TWD crew know who was killed (the writers, etc.). Greg Nicotero said that he's not even sure if the actor who is killed knows.