Welp! There it is. What more could you want? It's blue on the top... It says Wii U. I'm guessing we could have figured this out on our own, but Ubisoft went and spilled the beans for us. Then, later Nintendo responded to Kotaku:
Nintendo has finalized the design of the Wii U game box art, and many of our publishing partners have already incorporated it into their own game packaging. We are seeing those game packages online as retailers are starting to showcase their games. Nintendo-published game boxes will appear shortly with placeholder logos, and then ultimately with the final artwork for each game.
So yeah! Here you go: