If both the short-haired dachshund and the long-haired dachshund are purebred, then all of the puppies in the litter will be either short-haired or long-haired. This is because purebred dogs only carry the genes for their own breed. However, if one or both of the parents are mixed-breed, then the puppies in the litter could have a variety of coat lengths, including short, medium, and long.
In addition to coat length, the puppies in a litter between a short-haired and long-haired dachshund can also vary in other ways, such as size, color, and personality. This is because dachshunds are a diverse breed, and there is a lot of variation within the breed.