[The Ninth Valar]

From my reading of the Silmarillion, and recent listen to the audiobook before going to sleep, I have to concur that Turin's role is effectively finished as of his death. What comes later has not been revealed, according to published works, and even if the Second Prophecy was to canon, I think it meant that Turin will essentially be a hero of the final battle, not a Valar. He was created as a man, his spirit is that of a man, and his role would be to seek redemption for the failings of men, not gain immortality or great power. Consider it penance.