One thing that I think works against the "leaked photo" comment is that Nintendo has probably already been shipping Wii U systems to North America for weeks now ...
Nintendo is a "conservative" (read: cheap) company and they don't like spending money when they don't have to, and it is well known that they prefer to ship their systems through slow&cheap ocean transport than the fast&expensive air transport. It can take a couple of weeks for one of these transports to cross the ocean, a couple of weeks for the cargo to clear customs, and several days for the systems to be distributed to individual stores from their retailer's central warehouses. In previous years, when the Wii was in short supply, it was reported/speculated that Nintendo was using air transport in late November/Early December to ship systems to North America to take advantage of the holiday shopping season which resulted in (much) smaller shipments early in the new year.
Why you (probably) don't see leaked images of Nintendo systems like we saw leaked photos of the iPhone is that the market for leaked images of Nintendo systems is less profitable. I have no evidence of this but I suspect that a leaked iPhone image might be worth tens of thousands of dollars while a leaked Wii U image may only be worth a couple thousand. The market for these leaks really is based on page views and ad revenues of the site that leaks it, and a blog with a leaked iPhone image will probably have tens of millions of page views while a leak of the Wii U will have hundreds of thousands of page views; there are two reasons for this, (obviously) the console market is smaller and far more is already know about the Wii U when it goes into production.
