Yes! PJ and Howard Shore himself have all confirmed that he will return to do the Score for The Hobbit and the second film. According to Shore he has been working on ideas since filming of The Two Towers. Per Del Toro: “Shore is the VOICE of these films and will absolutely be invited back. Peter and Fran have talked to him a couple of times already and I’ve exchanged emails about the subject. He will return.”

Useful Links:
Howard Shore Confirms his involvement in The Hobbit
Howard Shore going There… Back Again