This is a shot in the dark, but what if, when Halsey is talking about how Locke will be ordered to “kill us both”, she could actually be referring to her and Chief? Locke could actually have orders from ONI as a Spartan. He could have been ordered to become a Spartan, and to end the current attacks by working with whoever and doing whatever necessary, but at the end, he still has orders from ONI to take out Halsey and Chief. Halsey for the obvious reasons, and Chief so that they can spin their web of lies like they did in Hunt the Truth by claiming that he was dead, and with providing “evidence” that he was a traitor. Obviously, they think they’ll benefit if Chief is gone as well as Halsey, so I’m thinking this will be a bit plot twist in Halo 6.