naruto is the true essence of rikudou. he embodies his will that the bijuus know and acknowledge.
even the juubi in this chapter recognized rikudou's will in naruto not madara and certainly won't be hashirama either since kurama didn't care for hashi. rikudou might appear after yin kurama is rejoined with yang kurama.
but seriously minato must be some prophet or he knew what rikudou was planning?