Currently Online 
During its first 18 first quarters, Switch moved 89 million copies
Meanwhile Wii moved 86 million copies in 18 quarters
The key difference is, on Q18 Wii was selling 1,37 million
Switch is selling 4,45
Wii moved another 15 million after Q8. If Switch start dropping off a cliff next quarter even 130 million would the absolute worst case scenario
Even if Switch keeps decreasing 25% YoY compared to 2020 (I will even make a 35% decrease for Q19 because Jul-Sep last years was monstruous), this would make:
Q19: 4,4
Q20: 8,7
Q21: 3,54
=16,6 million until March 2022, total 105,6 million copies. Then Switch would need to decrease at least another 40% YoY despite of its software pipeline and new model
Q22: 2,67
Q19: 2,64
Q20: 5,22
Q21: 2,12
= 12,65 until March 2023, total 118 million sales. Followed by another 40% decline YoY to make ~8 million/126 million for March 2024 and then 130 million lifetime
If this is your bet, you'd better start praying because the odds of those numbers turn to be real aren't big
