Some new information has come to light relating to the release of the Hyrule Warriors DLC costumes in the West. As it turns out, the costume packs will be free, as well as retail specific.
Those that pre-order the title with Amazon Canada will be getting the Twilight Princess outfits, while pre-ordering with Gamestop will net you the Ocarina of Time outfits. Update: It turns out that Best Buy offers the Skyward Sword outfits, which makes sense.
For some reason, the North American Amazon page for Hyrule Warriors doesn’t have the same offer.