It definitely depends on the direction they take if Master Chief is no longer a part of the games. Master Chief is not the entirety of the Halo universe. However, he is what brings us to Halo, so they can easily keep us all but they have to make the game sort of like it was with Master Chief, meaning a key character brings us back and is who we relate to. Personally, I’d be fine with Locke taking the spotlight, but they have to improve him a lot before that happens. I’m not done with the campaign, but he is too by the book and doesn’t care about anything but orders. What makes Chief so amazing is that he fights to protect humanity at all costs. He isn’t afraid to break a few rules or go against orders for what he believes in. Locke just feels too much like a simple grunt following orders, and that’s not interesting.