The Gamecube was a powerhouse in its day and at a great price but suffered due to childish image that didn't appeal to a more mature crowd and hardcore gamers. The wii u has incredibly weak performance and an inflated price. It's gpu is only marginally more powerful than ps3/360 and its cpu performance a lot worse. The wii u already performs badly and is under pressure in performance terms from quite humble android devices.
Most games actually run better on ps3 or 360 than wii u and thats only the few games that can be compared due to the wii u's small catalogue of games.
I'm just making the point that the wii u is far less competitive compared to the opposition than the Gamecube was in its day.
I think wii u sales will drop off faster because the hardware is so uncompetitive. It's the type of hardware that needs to create a large install base early in its life and create a large software base. In the absence of that I feel Nintendo will struggle to keep sales at the same level unless they price cut and even after a price cut I feel it will still drop in sales.
I'm a wii u owner myself but the reality is the wii u isn't a very good console, it has weak performance and a poor controller. It's only saving grace is Nintendo's brilliant games.
I predict 2-3 million sold this year and sub 2 million next year.
