If I understand this correctly. To get long coat puppies the mom has to be a carrier of the long coat gene. If she is than the puppies (regardless of sex) have a 50/50 chance of being long coat. I've heard people say they can usually tell if they are going to be long coat by 3-4 weeks of age.
GSD/Dinozzo (A.K.A. Jocose vom Mittelwest); Cats: R.I.P. Xena & Zora; Ferrets/Falkor, Draco, Drogon