According to VGChartz, Switch sales are up 77%YoY from 2019 and has sold 9.5Million through the first 24Weeks of 2020, which is unheard of for a Home Console with the closest one being the Wii, which sold 8.2M in first 24 Weeks of 2008
For comparison, it took the Switch 40 Weeks to reach 9.5M sold in 2019, compared to only 24Weeks in 2020.
Let's say the Switch keeps its 77%YoY growth for the rest of 2020, Switch sales would sell a ridiculous 34M in 2020 ALONE, never has been done by a video game system in history.
It's obviously unlikely the Switch will maintain it's 77%YoY growth for the rest of year, but even a more conservative 30% growth would put the Switch selling 25M in 2020 alone.
Even if the Switch had the exact same sales as 2019 for every week from this point out, the Switch would sell a really good 22M for 2020.
IMO 22M is the minimum of what the Switch will sell in 2020 unless shortages hurt it.