Adding a bundle without making it a special edition wouldn't do a big difference. If it was a customized Wii U the sales could have been higher.
In 2014 Wii U had a way better line-up than it had in 2013. It even had two of the strongest Nintendo franchises to help sell the console (MK and Smash), along with a Mario 3D World bundle.
Yet, all these great games didn't set Wii U on fire (a 30% something increase?).
Those numbers are not good.
If you ask me, i say they tried and still didn't manage to move enough units to make Wii U's future look brighter.