Naruto: main character I doubt Kishimoto would kill him. His purpose to surpass the Sage by coming up with a better solution to the tailed beast problem than the Sage did and to bring peace to the world since he is the child of prophecy. I suppose all of this could be achieved in his death but that's unlikely. However, Naruto also has to become Hokage, which he can't be if he's dead.
Sasuke: as the foil/rival to Naruto I doubt Kishimoto would kill him. Sasuke is the yin to Naruto's yang (I'm talking about their personalities and philosophies here) I doubt Kishimoto would kill Sasuke if Naruto would live and vice versa. So, I think they both will live. Sasuke must also live long enough to restore the Uchiha clan and prove that curse of hatred is not genetic. If he doesn't then Kishimoto would have one horrible Aesop on his hands.
Sakura: her purpose was to be the normal girl on the team. her chances of dying are greater than either of Naruto's or Sasuke's, but I still don't think she would die.
Kakashi: this death is most likely. His purpose was to be Naruto's teacher. He can't preform that propose anymore now that Naruto has surpassed him.