He still needs time to adjust to his new role. One year later doesn't really change much in terms of his growth. He might have started to resent Bron more if he stayed around. I think he knew mentally that he had enough of that role. Its a good role nonetheless and I think he is still very appreciative of Bron, but sometimes people have to find their own greatness and that is what he did. Personally, I don't see him coming back.