How much can the Wii U sell if Nintendo makes no bad decisions the rest of the Generation?

[ICStats]

I'm surprised Wii U has sold as bad as it has. I will probably get all 3 systems eventually.

As a primary console I think majority will pick from PS4/XB1, but some minorities will pick the Wii U, and some will pick PS4/XB1 plus a Wii U.
This puts the Wii U's role in range of GameCube.

My prediction is 20 to 30M lifetime for Wii U.  I think it will remain a secondary choice to PS4/XB1.  20M is a lower bound based on GameCube sales, but 30M an upper bound based on a slightly expanded market for Nintendo following Wii.