Everyone considered the wii sales drop to be too harsh. In my mind, if switch drops like wii, it couldnt manage to get to 140M.
So, I was navigating in the yearly hardware comparison chart (https://www.vgchartz.com/tools/hw_date.php?reg=Global&ending=Yearly)
I noticed Wii sales peak year (2008) was slightly behind switch's 2021, but I rounded to million floor for easier math, so I consider them the same.
And I did the math for Wii sales rounded down: +21M (2009), +17M (2010), +11M (2011) + 5M (2012) + 2M (2013) + 4M (rest+leftovers)=60M.
If switch keep this sales trajectory as wii 2009 was switch 2021, it will end above 160M.
It still manage to became the best selling console ever, according to this analyzis.
Then I made another analyzis, considering aligned peak years:
Switch peak year (2020) sold 1.175 higher than wii's (2008).
And this ratio predicted surprising well the 2021 switch: 21.05M (2009 wii) *1.175 = 24.7M, really close to 24.8M from 2021 switch.
So, I kept this ratio for upcoming years for switch yearly sales.
I got to around 47M more sales for switch, starting from 2022.
So, Around 150M.
Anyway, Wii didnt drop as hard as I had in my mind.
Disclaimer: Yeah, Switch will probably follow a different drop curve than wii's, it is just a thought experiment.