I updated the comparative thread with data from all three console threads. This is the graph, comparing the bets in all three threads (as of today):

You can still add bets.

20m

20-22.5 million. That's still crazy impressive sales for a console that is turning 4 next year. 2020 has been the hardware sales peak for the Switch though. I don't think Nintendo has the momentum to top it next year. But 20-22.5 million would still make it the second-best hardware units total for any year of the Switch.

I tend lean to 20 - 22.5 Million Units sold, still don't know how many people own both Regular Switch and Switch Lite.

My guess is slightly above 25million.
It's hard to imagine NSW dropping more than 10% next year.

The massive Covid boost wont continue but how much will it dip, it will come down to whether covid created sales or simply pushed sales forward.  

With Switch accelerating it's dominance in China, Japan, South Korea and Taiwan, while re-entering Brazil - you folks seriously expect it to be down 5 million units YoY?

2021 > 2020

Couple of factors:

• Q1 2020 was underwhelming due COVID disrupting the supply-chain, even in Q2 2020 Switch continued to have supply problems across most markets
• Ring Fit & New Horizon continue to attract new users
• China sales are accelerating in just a week in one retailer there has been over 1,000 reviews for Ring Fit Adventure Bundle, the game only launched officially in September, New Horizon hasn't even launched officially in China!
• South Korea & Taiwan combined are selling more than France did in 2019
• There was no big games since the New Horizon launch

2021 will fix some of these problems

• Q1/Q2 2021 will up YoY because there is no supply problems and major markets like China & Brazil will start to contribute
• Q1/Q2 2021 also have far greater support announced by 3rd Parties - Monster Hunter Rise, Story of Seasons, Rune Factory 5, SMT V, Bravely Default 2 are all games that will push Switch in Japan and Asia - compare that to this year when in the first two quarters... *checks notes* we had One Piece: Pirate Warriors 4  
• Lastly in the fall we are likely to get one big Fall Nintendo title and one big Pokemon title - something we lacked in 2020

Correction

People here are expecting it to be down 10 million* YoY

OK, last days to place or change your bet. I graphed the current bets for all three consoles (in three threads):

People see Switch above 17.5M apparently.

You can still change your bets until the year ends.

VGC says: 25,015,,809. So just barely into the >25M category.

I don't think payouts for this were triggered yet, can someone do that @axumblade @TruckOSaurus ? And sorry for the spamming of mentions...