As of March 31, Nintendo has sold 6.17 million Wii U consoles worldwide. The company expects to sell another 3.6 million systems by the end of its fiscal year on March 31, 2015.

That's our real secret sauce [the Gamepad], it is the only real innovation in this console cycle, it's the only real new idea or game experience and with Super Mario Maker it shows you how magical ...

As such, "the development just never proceeded" and, with the Wii U becoming a rather short-lived console in the grand scheme of things, dual GamePad support just "never came to pass".