It's going to be difficult. No doubt it's going to beat the Wii and the Game Boy, but reaching the +150m threshold is something completely different. For that to happen the Switch needs either a very long lifespan or a massive software output that keep the numbers going high. In regards to the lifespan, we could still see a couple of revisions to keep the numbers going (a cheap home console only version would sell well, a Pro version is more difficult but not impossible). And software-wise, the fact that Nintendo can concentrate on a single platform for the first time since the NES days is helping, but most of the heavy hitters are already out. Mario Kart, Smash, two 3D Marios, Pokemon, Splatoon (soon to be 2), multiple Zelda games, Animal Crossing... There are some things still left, but most of the console sellers are already out.
Yes, and no.
We didn't get another 3D Mario (neither the Super Mario 3D All Stars collection nor 3D World and Bowser's Fury is "another 3D Mario") so there is still room for this to happen. And we al know what "3D Mario" means, it means 10+ million sales, 97 on Metacritic, an redefining what a great game it is. We didn't get this since Super Mario Odyssey, and I am still hoping for Odyssey 2, just like Super Mario Galaxy 2 was way superior to Galaxy 1.
And we'll get an open world Pokémon game, which is requested by the fans for ages.
And Splatoon 3 was anounced 2 months ago, so I don't understand your point about Splatoon 2.
And regarding Zelda games, we have a second one coming, aslo anounced.
And Metroid Prime 4 of course, and Bayonetta 3.
And I still believe Mario Kart 9 will happen. Not now, since the sales momentum is tremendous, but at some point.