I'd dance in the streets if a Zelda game ends up that high.
I sadly don't think this'll happen however, I think you're too optimistic from next year onwards, maybe even this year onwards even. I also doubt they gave the WiiU version another shipment, so it shouldn't be much higher than the number we already know. It keeping up with Mario in Japan is interesting though.
I hope this would happen, but I think we can be happy if the game gets to something like 12m on Switch. That would already be amazing.