1 : WHO really, who doesn't have a Switch, and who was not enough interested by Zelda, will suddenly think : "omg the new sequel of Breath of the Wild is awesome, I want a Switch !!
well, I have an answer : me, so far I only have the Wii U that I bought in end of 2017 just for Zelda, but we are marginal in this situation.
2 : You mean like ARMS and Astral Chain ?...
You've not helped your own argument with the Zelda example here because BOTW has sold more than any other Zelda game before it meaning people who had no interest in the games before bought the Switch to play it. Before BOTW the series averaged 4m your logic would have dictated not more than that would have bought the game now the new game is going to pass 20m even over 2 years on meaning it's selling to people who weren't interested in the series before hand this can snowball onto the sequel the same way Modern Warfare did for the Cod games and GTA3 did for the games that came after it as people who didn't try BOTW can be interested as the huge success gathers more mainstream interest.