It would be a miracle if it dropped now

Really, that's just not a realistic probability.
Puppies testicles should be in place by 6 weeks of age, and certainly by the 8 week mark. A few do descend later than that, but only so much later. At around 4 months, the inguinal canal through which testicles descend closes. Permanently. Whatever side of it the testicle is on at that point (abdomen or scrotum) is where it is staying. The only possible hope of a testicle descending beyond this age is if the inguinal canal failed to close normally. And whilst I've heard of plenty of people hanging on, delaying neutering their dogs till six months, even a year of age in the hope the testicle will magically appear - I have never yet heard of one doing so. In short, I'd say that the chance of a missing testicle making an appearance in a 7 month old pup is incredibly small.
The risk of torsion isn't that small though (the retained testicle twisting, or wrapping around other organs - both of which are lifethreatening). Neither is the risk of cancer of that retained testicle if he isn't neutered. Above all, this animal must not ever be used for breeding - because cryptorchidism (retained testicles) is hereditary. Here's a short veterinary article on the condition that you may find useful:
http://www.peteducation.com/article.cfm?cls=2&cat=1630&articleid=897 If neutered though, he would have absolutely no health risks arising from having been cryptorchid.
LOL - edit to say that the poster above has the first ever case I've heard of of a testicle dropping that late. Many, many people who've waited in vain for it never to appear - but that's the first time I've ever heard of it actually happening.