What do you guys think? Currently I could foresee the Switch being close to DS numbers in NA, Japan and easily surpassing the DS in "Rest of the World" region. However, I'm noticing the potential Achilles heal for the Switch that might prevent it from surpassing PS2 or DS sales is Europe, where I haven't yet seen the Switch blow up to DS sales numbers in sales and the Switch is currently at a decent deficit against the Wii. While it seems likely the Switch will still outsell the Wii in Europe by having a longer lifespan the Switch isn't showing many signs that it could sell well over 40 Million in Europe. Which would keep in relatively far below the PS2 and DS which sold 50M+ in Europe.

The DS sold 11 Million Units in it's best year in Europe while the Switch in 2020 sold 7 Million in Europe, which is widely considered the peak year for the Switch. So unless the Switch still has yet to reach it's peak year or has a much longer lifespan of sales than the DS then I find it unlikely it could sell over 40 Million like some are speculating. We have to see.

I see the Switch selling 38M in Europe.

45-50m

I don't think Switch has hit its peak in Europe yet. There is still a lot of room to grow there.

I think 40M are reachable :)

I agree with OP’s analysis. Although it will be interesting to see if 2021 is in fact peak year for Switch in Europe.
At the moment I don’t see Switch having the long lifespan of the gameboy in Europe that would get it to 40 million, but I’m happy to see that people agree that it’s at least on track to beat the PS3 by a comfortable margin. I’m tipping 36-38 million. Enough for Nintendo to maintain a strong foothold in Europe and give Nintendo’s successor a strong chance of launching successfully in what will by then be a dominant PS5 market, but still have room for a more portable machine. Much like how the PSP found a way to do well in Europe despite tough competition.

To be honest I’m still excited that Switch is capable of doing more than 35 million in Europe against a dominant PS4. That kind of number seemed impossibly optimistic before the Switch launched.

I don't think the Switch will have a much longer lifespan than the DS, but I definitely think it will be longer. There was only a bit more than 6 years between the DS and 3DS (almost 6 years exactly in Europe), I expect that period to be at least 7 years for the Switch. In regards to peak year in Europe, I think 2021 has a chance if it gets a price cut, though it still won't come near the 11 mil of the DS. The DS did sell a ridicolous 52 mil in Europe though, so the Switch doesn't need to keep pace with that to hit 40 mil.

It's not a sure thing, but as of right now crossing 40 mil seems doable to me, so I voted for 40-45 mil.

43M is what I think

I personally think it'll do around 40M, if it is short it won't be too short, and if it is above it won't be too far above. I concur with Rolstoppable that last year wasn't necessarily the Switch's peak year in Europe. Especially should their be a price cut.