when will Wii U pass 7m?

[Barozi]

September is the time sales pick up, so probably there.
MK8 will surely sell some hardware, but if you're a Mario fan you should already have the console.
SM3DWorld and especially Donkey Kong showed that many Nintendo fans already bought the console near WiiU launch, because they knew that these Nintendo games would follow eventually. (Titanfall for XboxOne was a similar case too)