As we know, someone is going to die at the end of season three, we also know from various interviews from the cast and from NYCC that Peter won't die, he won't be trying to be an Alpha again until season 4.
Derek/Tyler Hoechlin maybe cast in Arrow (maybe even as Night Wing is my theory), it is a rumor that's been mentioned with Colton Haynes on Twitter back in December.
Since 3B It's been foreshadowed that Allison may die or even Lydia by Allison's hands. Crystal Reed has said that someone dies from the season 1 cast and it's very emotional for everyone involved because they are like there own little family. I have this gut feeling that Allison may die because Kiera will fill in her spot as the badass female huntress chick. Also, Kiera has been one of they most liked newest characters in the show.
Derek may just die because frankly all of season 3A the Alpha Pack was trying to kill Derek/make him join the pack. Derek as I said, may die and go onto Arrow, it is a possibility.
Lydia isn't likely to die because she's been developing her banshee powers, it would be useless to have developed her now to just kill her when we finally know what exactly is going on with her.
Stiles is a fan favorite, if he were to die the ratings would most likely plummet. Stiles may just become a werewolf by the end of the season, they could end it with him being stabbed with Kiera's katana and Scott's claws and do some dramatic fade to black with us getting a flicker of Stiles eyes changing to gold.
Melissa was a theory of mine in 3A but now I'm not exactly sure if they'll kill off Mama McCall. Sheriff Stilinski, why would you even think that?!?!
Chris Argent, Allison already lost her mom, are we really going to make her lose her dad too? I mean no parent should ever have to burry there child but I'd rather have that type of pain than Allison literally having no family but Gerard left.
Isaac is a possibility to die but if he's from season 2 why would they kill him off now? Yes, like Derek his death is always foreshadowed/his life is always in danger but they've tortured him enough for this season.
So, this is my theories, what is everyone elses?