Lets see if the switch can do what the wii u could not, and what the gamecube barely did-make it past 20 million units. I think the switch will sell 4-5 million in 2017, 5 million in 2018, 4 million in 2019, 3 million in 2020 and 2 million in the rest of the future. I do not think the switch will pass 20 million units sold.
I believe ps4 + ps4 pro will sell 150 million units and xbox one + xbox one scorpio will sell 90 million units in contrast. I believe the pro and scorpio are "future proof" and will be on the market for the next 8 years.