Radio Shack may have shown its eagerness to account for the iPhone 5 with inventory listings for several models. The retailer lists versions for Sprint as well as for AT&T and Verizon, 9to5 showed. Each version also had 16GB and 32GB versions.
The entries aren't necessarily confirmations. Retailers are sometimes known to put entries in as placeholders so that they have a frame of reference for pre-orders. Mentioning Sprint is unusual given that only AT&T and Verizon are confirmed partners, however, and suggests Radio Shack is anticipating the third carrier.
Radio Shack is one of Sprint's preferred retail partners.
With multiple instances of new iPhones showing in inventory, signs are mounting that retailers expect to carry any new iPhones comparatively quickly. Most have pointed to October 14, but an earlier release hasn't been ruled out.