The new update to the Amiibo section of NCL's website lists Zelda, Sheik, and Toon Link as compatible with Hyrule Warriors, and the latter also compatible with Mario Kart 8.
While I'd assumed Hyrule Warriors would be compatible with the rest of the Legend of Zelda Smash U Amiibo, I wasn't sure if Nintendo would continue to roll out Mii costumes for future Amiibo.