This has been a strong rumor for a a few weeks now, but I was hoping it wasn't true. Middleton was one of my favorites on the staff. If he does go to Duke though, Saban will replace him with another top notch coach. As far as special teams go, BAMA coaches them a little differently than most other schools. The Tide has several coaches that are heavily involved with coaching special teams, but Middleton was the main dude, and a good one. Like Terry alluded to, if his wife was not in poor health (she has MS), he'd still be coaching ST's in the NFL (at Tampa). Gruden loved him, and only let him out of his contract (to come to BAMA) because of his wife's situation.
With whatever he decides, I wish nothing but the best for he and his family.