Whether it sells more than 80M units depends solely on whether Nintendo can hold interest for such a considerably long time. So far, even with its lackluster 2018 is currently having its release input, the machine has been holding up nicely, and Smash should provide a great effect not only during the holidays, but throughout the next few months to come as well. What comes after it, though? Well, Pokémon is a given, but hopefully they can bring up a new Mario, Zelda, Animal Crossing, new things, etc., soon.
My bet with The_Liquid_Laser: I think the Switch won't surpass the PS2 as the best selling system of all time. If it does, I'll play a game of a list that The_Liquid_Laser will provide, I will have to play it for 50 hours or complete it, whatever comes first.