Brown had a solid spot on the team when this teaching was happening and Porter now has a spot on the team. However, don't expect Porter to completely transition to a mentor spot. He stunted Cameron Wake's development last year somewhat and refused to take himself off the field in some spots. In fact, my biggest concern with Porter is that he is going to slow down Davis and Cody and be much more concerned with his own PT.
Miller is a different story, he is a few years older than the guys he is competing with and has never had to be a mentor, so I don't see why he would start doing that now. Also, he would be clinging on to one of the last few spots so it would probably be against his best interests to help anyone out who would potentially leave him jobless for the 2nd year in a row.