Do we know how much they sold last year?

people are underestimated Smash Bros Ultimate abilities to push hardware sales.

4-5(physical+digital) Million seller opener this year December vs 200k opener(xenoblade 2) in the last December. Cyber Monday week isn't going to stop Smash Ultimate madness.

LTD 21 months
PS4-8.38
XBO-7.66
NSW-8.73
3DS-6.40

You do realize black friday is all about deals ? 

Switch was still 300$ but with a game while PS4 was 200$ with a game or something. It doens't take rocket science to know people will jump on the bigger deal. 

Not cause it's 5 years old that it won't perform on sale driven holidays. That 5 years handicap will hit once we have the december numbers, i'm sure Switch will be leading by a very comfortable margin. And again, PS4 is down YoY while having better first party this year, so yes, it's clearly getting old. I think it will take a moderate hit next year as i don't see them having other big system sellers like a Goty/Spiderman/Monster Hunter.

Also, Nintendo never had huge numbers during black friday, these Switch numbers are insane for them and blew out the best 3DS ones. So yes, this is a big achievement for the Switch.

All three had another great month. Congrats PS4 for another win. Switch got a big yoy increase which is awesome to see. Though I think the biggest surprise is Xbox only being 3% down. I thought it would go down by about 20% due to not shipping new hardware this year, like they did last year.

I think the Switch will sell 2 million units next month, giving us the biggest december of this generation by any console.

In the system seller category, they'll have Kingdom Hearts 3 and maybe Last of Us 2, but I agree.
This Black Friday, Sony was basically selling the system at $140 (less than half its MSRP) plus one of their biggest and best selling exclusives, which was also their most recent one. And while it definitely had the results they were hoping for (~1.09 million increase. The system's biggest one yet for Black Friday), it was still below last year and now we're going to see a pretty steep drop. The PS4's best years are behind it. Kingdom Hearts 3 may help it be flat YoY or slightly up in January and February, but from March onward I think we're going to see a noticeable and obvious decline. Nothing too drastic, but its baseline will likely be at the same level or slightly above what it was in 2014. 

And here I was thinking the 5 year old consoles would carry on selling better every year and only improve when talk of the PS5 and XB2 suggested they could be coming next year ... It's amazing to see the new console selling better too. I fully expected it to drop YoY, especially in light of the fact no mention of Switch 2 coming next year as emerged ... I'm surprised by this 'every single generation' ...

Things will get ugly next year for PS4 and XBX1 hardware. Switch on the other hand with Metroid Prime 4, Animal Crossing, NSMBUD, FE 3 Houses, Marvel UA3, Yoshi, and the biggest exclusive in this generation Mainline Pokemon Game plus rumored new hardware revision are going to make Switch explodes in the 3rd year.

Call me optimistic but I think that if they drop the price low enough ($250-350 for PS4/pro and $230-400 for X1S/X) both machines will be able to match this year's numbers.

Benji already said in era thread, a price drop isn't going to stop imminent YOY decrease for both consoles for the next year and Matt(npd) already said the thing about doom and gloom for hardware with an exception to Nintendo Switch.