Thing is. How many of those people own a Wii U AND a 3DS? Because I'm one of those people, and I sure ain't buying the Switch twice. I think it's possible that it can reach or surpass the 3DS, but I think anything past the 75-80 million is wishful thinking during this initial stage.
Hardware Comparison Threads:
Current Thread
Is Hardware Getting TOO Powerful?
Older Threads:
PlayStation/Xbox/Switch: 2022 Edition
PlayStation/Xbox/Switch Hardware Battle: 2021 Edition!
PlayStation 4/Xbox One/Nintendo Switch: 2019 vs. 2020
PlayStation 4/Xbox One/Nintendo Switch: 2018 vs. 2019
PlayStation 4/Xbox One/Nintendo Switch: 2017 vs. 2018
PlayStation 4: 2015 vs. 2016 vs. 2017