I don’t know if this has been said before, but here we go. My theory corresponds with what the sprint video portrayed. Obviously Chief is they main character and the main character of the franchise. What if eventually he pursuades Spartan Locke in to understanding why he is doing what he is doing by going AWOL. What if something happens to Master Chief and everyone thinks he is dead but Locke knows he is alive and tells the UNSC that Chief is dead even though he really isn’t so Chief can finish his task. Maybe both Osiris and Blue Team thinks he is dead but some how Locke saw chief and he is still alive. Just a theory, let me know what you guys think.