He sensed that the hidden leaf village was impossible to defend against the Otsutsuki so he put himself on a secret mission to start a new Anbu. Im expecting him to show up some time soon. With the possible loss of Naruto and Sasuke looming the village lacks leadership. It would be a good time for him right now. He's always been clutch it makes sense right now. He could possibly have a new dojutsu similar to Ishiki's. It could possibly be the Shin clan's first generation that plays a major part in saving the village. They're the only ones who can use s/t jutsu. S/t jutsu is needed to get there and save them. Naruto and Sasuke will need a refuge. Koji comes back too.