GameStop advertisement suggests pre-orders may be available soon.
http://www.nintendoworldreport.com/rumor/31286
GameStop may begin to take pre-orders for the Wii U as early as August 13.
GenGAME recently reported on an image of what appears to be Wii U advertising in a GameStop. Citing "good relations" with GameStop management, GenGAME insists that the image is legit and that the advertisement campaign should begin on August 13. Furthermore, the article indicates that pre-orders will likely be available the same day the promotion begins or shortly after.
We called a few GameStop locations this morning, and while none are currently taking pre-orders, each store made it very clear that the day Nintendo announces a release date for the Wii U, they will begin to offer pre-orders. If GameStop is indeed beginning a big advertising push for the Wii U next week, it might indicate that Nintendo is close to finally revealing release information for the upcoming console.