It may not have the insane demand of the iPhone 5, but Wii U is apparently doing quite well for itself. Ever since its coming out party last week, retailers were quick to offer pre-orders for Nintendo's next-gen system. If you sat on your hands, you'll have to wait for another round of pre-order stock. Already, many online retailers have sold out of their initial estimated stock.
As MTV Multiplayer pointed out, various retailers no longer offer Wii U pre-orders. Best Buy, K-Mart, Sears, Target, and Toys R Us are sold out entirely. GameStop has sold out of the Deluxe version, but the Basic model is still available. Wal-Mart still has stock for sale, though that may not last. Amazon hasn't listed the console for sale yet at all.
Chances are retailers will have more pre-order stock available some time before the console's November 18th launch. But if you don't want to take your chances on eBay come launch day, you may want to pre-order the system at your local retailer.