i know halo 4 couldnt have been to long after halo 3 because cortana was still there and wasnt to insane or corrupt to have to destroy herself. also john couldnt have been frozen for too long because of how quick he was moving. anyway, my prediction is that john is inside of the micro dyson sphere or whatever the hell its called (its been awhile since i read onyx) or the blue thing he is going towards is a portal to go to the shield world that halsey and the spartans are stranded on, which is a better explanation on whats happening.