Right, but I still don't think anything in the Sandshrew line would feel right. There's nothing special about Sandshrew. The Unown are special, Slowking is psychic and could "talk." An evolution of Ninetales would would work, way back in the anime a Ninetales created illusions and talked through an illusion of her owner. Or it could be something else, that's just one that I think could make sense.
Well think about it, Slowpoke wasn't anything special either, yet they made Slowking for some reason. They turned a mentally challenged Pokemon into a genius, so maybe they'll turn Sandslash, a Pokemon good at digging, into Sandperior, a Pokemon good at performing open-heart surgery.