EDIT: According to Gametrailers, they recieved word from a Ubisoft representative they told them ‘ “Why yes, the Wii U box art you sent is legit; in fact, it’s too legit to quit.” ‘ Source
While the evidence points to all this being true, we await a response from Nintendo themselves to confirm or deny (most likely deny) whether these box arts are the real deal, so we cannot confirm anything as of yet.
Through a drought of Wii U news, Amazon.ca may have leaked the official Wii U box arts, being attached to the ‘Assassins’s Creed III’ page, the ‘Avengers: Battle for Earth’ page and the ‘Just Dance 4’ page. Now these could be any old mock-up but the Target online store has also provided the same box art for Assassin’s Creed III, along with the look of the spine of the box. The Nintendo Network logo is placed on the boxes and the banner seems reminiscent of the Gamecube days, but what is most puzzling is the use of either a yellow or gold stripe along the bottom of the banner. Now it might just look yellow in the render and be shinier and look a little different from a real perspective, but we can only wait. Scroll down for a look of the boxes.