I always thought it was the poor software support that caused the Wii U to flop. The console won't even be receiving it's first signature flagship title after 4 years of release, with Zelda U.
By contrast, the Wii had dual signature flagships on launch day: Zelda: Twilight Princess and Wii Sports bundled in; and Super Mario Galaxy, a third flagship joining the battle, by the end of the first year. Along with 16 other titles including Smooth Moves, Metroid Prime 3, Fire Emblem Radiant Dawn. The Wii also had an interesting, fresh, and intuitive interface. Say what you will about the Wii, but Nintendo never hit so hard and fast as they did with the console in that first year and half (Mario Kart, Wii Fit, Smash came in the first half of year 2); the Wii U was relatively slow and weak by comparison.
Nintendo probably the Wii U a long time ago. They coasted through by spreading out the initial wave of software development, along with derivative franchise software, ports, and publishing third party software. Their dev capacity has been mostly silent since year 1 of the Wii U launch. Probably because they're developing software for Nintendo's upcoming console codenamed The NX (Nintendo Cross).
Around two years ago, the first probable NX details leaked -
http://nintendonews.com/news/general/ni ... ware-name/ I argue probable, because all details that Nintendo has officially released have supported this concept. The NX should be unveiled in the next few months, and speculation is high that we'll be seeing it released by the end of this year.