Where would SSS tier begin? 200 million units? Possible for Switch, but not a sure ting.

There is still a long way for that. If Nintendo announces Switch 2 next year and releases it in ~2 years (backwards compatible to Switch 1 plus new games exclusive for Switch 2), Switch 1 sales will probably go down after the announcement.

Several consoles in the past have kept selling significantly even after their successor has been released.  So even if Nintendo moronically announces a new system next year (beyond unlikely), then that will not be enough to kill Switch's momentum.  They have far too many games releasing on the Switch for momentum to "drop off a cliff".

Software is ultimately what drives hardware sales.  Did you know that Sega of Japan tried to kill off the Mega Drive/Genesis, but it still kept selling anyway?  They really wanted people to buy the Saturn, and yet the Genesis kept selling for several years even after the Saturn launched.  The Genesis's software was too good and too plentiful, and it kept driving hardware sales.

And several oither consoles in the past didn't keep their momentum despite "having far too many games releasing on them". Where was the momentum for PS3, Xbox360, Wii, DS, 3DS, PS4 after the announcement or launch of their successors? 

SSS tier would be over 200 million. Not happening, not a chance.

Yes, the Switch sales won't drop of a cliff, that shoukd be clear, but it won't be easy to top the DS and PS2 regardless. But it's still possible.

This is why I don't like predicting so firmly. You just can't know. 

Most of the consoles you listed lost their momentum before their successor was announced.  

You've confused the cart and the horse.  A loss of momentum leads to a successor getting announced, and not the other way around.

Sure you can. For example, you've already lost the bet in your sig.

A loss of momentum is only one aspect of the announcement timing. A new console generation has to be planned years in advance.

There is a "point of no return" long before the announcement and in most cases before the momentum is gone. The main hardware specs are set in stone, contracts with APU-manufacturers (AMD / Nvidia / Intel) have to be signed, production capacities for the APU has to bee booked (TSMC / Samsung / Intel), first party developers and selected third party developers have to be informed about the specs, features and launch window, so that they can work on their launch titles...

Of course the planned launch date can be shifted for a few months (f. e. PS3 due to their Blu-ray-laser problem), but not for years just because the current gen still sells great.

And as I wrote, I see 200 million units possible for Switch, but not a sure thing.

The 3DS was announced in March 2010 (and gameplay was shown at E3 2010), even before finishing the fourth extremely successful NDS year (FY3/2007 23M units, FY3/2008 30M units, FY3/2009 31M, FY3/2010 27M units).

If the Switch has a similar trend from now on (FY3/2020 21M units, FY3/2021 29M units, FY3/2022 ~31M, FY3/2023 ~27M units), a "Switch 2" could be announced in the first half of 2023 and launch in Q4 2023 or Q1 2024... that would already be one year better legs than the NDS. If the sales drop after the announcement similar to NDS, that would lead to scenario A, where Switch would probably beat NDS and PS2 with 160M  - 170M units (if price drops happen similar to NDS + PS2, especially for the entry model).

If Nintendo can keep up the momentum another year and the "Switch 2" gets announced in the first half of 2024 and launch in Q4 2024 or Q1 2025 and sales drop after the announcement similar to NDS, that would lead to scenario B, where Switch would have lifetime sales of 190M - 200M units... still in Tier SS.

Your "Tier SSS" scenario ain't that easy to reach, it would involve keeping up the momentum more than two years longer than the NDS and probably a few price drops of Switch and especially Switch Lite. Not impossible, but also not a given.

If Nintendo can keep up the momentum another another year and the "Switch 2" gets announced in the first half of 2025 and launch in Q4 2025 or Q1 2026 (do we really want to wait that long?) and sales drop after the announcement similar to NDS, that would lead to scenario C, where Switch would have lifetime sales over 200M units.

No need to reset.  Ryng has done a great job with updating a snapshot of the Poll at the end of every year in the 2nd post of the thread.  It's interesting to see.  Especially in the case of people who are still voting PS4 even after December 2020.  I'm not sure exactly when I voted, but it had to have been quite a while ago.  When this thread got bumped yesterday my Hot Topics list showed it as having hundreds of new posts since last time I read it, and it showed that I selected "Switch by a small margin" as my prediction from that time.

Nah. If the world suddenly stops within the next two years, I'd have won. I trust the process.