You can have that luxury because really if you're wrong it's not skin off your back, you can just say "oops" and move on with your day. if you're running Nintendo you don't have that luxury you have to take into account not everything is always smooth sailing and have a plan for that scenario.
And how is it a theory from 2017, Nintendo has several large selling IP like Pokemon and Animal Crossing and B-tier stuff like Fire Emblem that weren't available in 2017 or 2018. Even the GameCube didn't peak in sales in year 1, so that's not really a relevant point.
They need to start planning for Switch 2 really like now. Estimating a 3 year cycle for game development, you need to know what you're doing now.
Planning for it, yes. But panicking and rushing onto a new system prematurely is a dreadful idea.
Bet with Liquidlaser: I say PS5 and Xbox Series will sell more than 56 million combined by the end of 2023.