I'm not really worried about Mario 3D World in the long term per se, worldwide. I'm sure when all's said and done Nintendo will be able to push its sales up to 4+ million WW, which will make it nicely profitable.
It's the whole "Wii U haz no games, you can't judge it, when it gets games like Mario 3D, then you will see a big explosion in sales!" folks that are probably getting the wake up call.
Mario is gonna be alright, it's the Wii U as a platform that is more of a concern.