Probably not, but it could well get within 10% of doing so which is extremely impressive.

I dont think so anymore. I think it will come within 10 million of the PS2 though. 3rd place is still amazing.

I really don't see them releasing a new console in 2024. This might be the impression you get when looking online, but that's a small bubble, sales indicate that it is still a console in high demand, just no longer in insanely high demand. Selling around 20 million in a year is extremely good, yet a lot of people (content creators) are saying that the switch is finished and needs to be replaced. The 3DS sold around 7 million for 4 years, just because a console is dropping in sales, doesn't mean it is going to keep dropping the same amount every year. Nintendo has reiterated every year that they want a longer lifecycle for the Switch. They entered unprecedented territory for themselves as they are looking to maintain sales instead of looking at new hardware.

Every new console is a console on it's own, the success or perception of a brand is of no importance. This should be clear by the sales progression of Nintendo's latest consoles.
GameCube - Wii - WiiU - Switch
The success or failure of the previous console had no impact on future consoles. I also don't think saturation plays such a big part at this point. Consoles stop selling because support drops and newer hardware is released. Keep pumping out games and sales will remain comfortably profitable for longer than we might assume.

If Nintendo were to release Super Mario Movie: The Game, Luigi's Ghost Town, Pokémon World, Donkey Kong 3D, F-Zero XXX, Dreamcast/GameCube/DS/2DS NSO apps, Xbox Live service, Animal Crossing: Planets, Mario Galaxy 3, New IP's (survival, roguelite, fps, crafting, battle royal), Xenoblade X-X2, New Nintendo Selects line, Mario Party DLC, Mario RPG 2, OOT/Majora remaster, 2D Mario, Astral Chain 2, Pokémon Legends 2, Mario Maker 3, Oracle/Ages remake, Switch Pro - decrease in price of previous models, Metroid Chozo Spin-off, Wario Land 5, Waluigi's Empire, Bowser's Adventure, on top of Tears of the Kingdom, Pikmin 4, Prime 2-3-4, Wind Waker HD, Twilight Princess HD, Professor Layton, Baten Kaitos I-II, Advance Wars Reboot, Mario Kart DLC and whatever else they are realistically releasing this year and next, would we honestly think sales would drop another 5 million both years, bringing it down to 10 million in 2024? I doubt that.
It's an unrealistic list of games, sure, bit only to point out that saturation only happens when the console loses support, new games bring in new people.

While I do hope and expect some form of backwards compatibility, I still also expect Nintendo to do something crazy again with the hardware, they are not in the habit of only increasing power. This would also leave room for one more Switch hardware iteration to be released after the summer of this year as a definitive way to play the games on a Switch console. Keeping in line with the 2 year refresh they have been doing so far. I'm hoping for some sort of wearable dock so I can lay down and play without straining my arms, but I won't hold my breath :P

Well PS4 got a handful of awesome games in 2020 (Last of Us Part II, FF7 Remake, Ghost of Tsushima, Persona 5 Royal, Dreams, Fall Guys to name a few) but it sales were lackluster (it shipped 5 million in 2020 in total if I recall correctly).

So even with 8 1st party/exclusives the Switch is releasing this year (that we are aware of), including 2 highly praised games (Metroid Prime and Zelda TikTok), it should be ending the year with 15 million units sold at best (which would make the total at 137 million, which is still very impressive).

The thing is it won't be around 20 million this year, it'll be around 15 million and drop even more next year. A lineup that strong would soften the drop a lot sure but as you said it's unrealistic so a realistic lineup should see it drop to 10 million next year. Nintendo's investors would get very unhappy if they don't release it next year so at this point 2025 will only happen if they really need some extra time to get games ready for the successor.

The Playstation 5 had a big reveal event in June 2020, was already known about before that time and released in November of that year. They had moved on already. I can agree with the 15 million for this year, the point is that there's no guarantee it is going to keep dropping by a significant amount every year if they keep supporting it and not announce a new console.

The ''around 20 million'' was for the past year, as it hits close to 19 million if I'm not mistaken.

That part of the comment was directed at a saturation comment, pointing out that saturation will not occur if support remains as high as it was in 2017. Saturation occurs when support for a console is finished, no longer anything new to entice new players, hence eventually everyone who wants one will have bought one, ignoring yearly population growth. New software will keep enticing new players. Spread out my list over 3 years and it comes down to about 1 big game every month, which is really not unrealistic for a console when fully supported. Besides the obvious wishful thinking with a lot of these titles, it's only unrealistic because we don't expect Nintendo to continue providing such massive support.

Your last comment is based on absolutely nothing though. Why on earth would investors not be happy if they don't release a new console in 2024? They only care about profit, so as long as Nintendo is making profit, they will be happy. Just because some content creators or the absolutely tiny online community are hunkering for a new more powerful console, doesn't mean the general public is. They are clearly showing interest in the current console, as Nintendo has also pointed out with a high engagement over the past months.

There's a limit to how many new players can be enticed though. The vast majority of people who'll ever buy a Switch have already bought one at this point so new software can only do so much to slow down the decline now. 

My last comment is based on things such as Nintendo's stock taking a hit recently due to them cutting their forecast due to lower than expected demand. The investors will obviously be unhappy if Nintendo lets hardware and software sales decline throughout all of 2024. Public interest in it is clearly in the decline phase now.

If Nintendo does some aggressive price cuts... Which is absolutely more than possible considering it's archaic hardware and ancient fabs that the chips are made on... I don't see why they wouldn't be able to kick sales up some more.

Could you imagine how well the Switch Lite at $149 USD would do? Especially in the current economic climate? Do some digital game bundling, maybe even drop it to $99 USD during the silly season. I.E. Black Friday, Christmas etc'.

Selling another 40 million at this point would still mean that the majority has already purchased a Switch. I'm not saying it's going to keep selling 20 million every year, just that a decline doesn't have to be at a steady pace, hence my example of 3DS selling 7 million for 4 years, it didn't drop lower until the Switch was released. The Switch is in a much healthier position than the 3DS, so maybe it can sell 12 million for 4 years until a new console is released. I'm not saying it's going to, just that with proper game support, price changes and hardware iterations and not announcing a brand new console, it's possible.

Investors will be unhappy if Nintendo doesn't do anything, but why would releasing a brand new console be the only solution? The Switch just sold 19 million last year and software sales are basically flat, decline is very relative here. We've just been spoiled by the insane numbers it has been doing. People are acting as if sales dropped below 10 million and they better hurry getting out a new console or Nintendo will be irrelevant. 

I don't think that sort of scenario is possible, there's just not enough people left in places like Japan without a Switch to keep it going that high for that long. Europe is relatively untapped but Europeans aren't as into the Switch as people from NA and Japan so they'd need to cause an surge of interest there somehow and I'm not sure how they suddenly could.

Software sales were only down slightly but are gonna start declining quickly now based on their forecast for this quarter and the evergreens slowing down so the ideal business move is getting the successor out once they've gotten a lot of use out of the high install base but not waiting too long to where they have multiple poor quarters. And it wouldn't be hurrying, November 2024 is still nearly a full two years away. 2023 would be hurrying but 2024 would be a good pace since to compare it to the PS4 it peaked in 2017 and the PS5 released 2020 so the Switch peaking that year and the successor not coming till 2024 would be an even longer gap due to its higher sales peak than the PS4.