We don't know how long Nintendo will continue Switch production, there are analysts that expect Nintendo wants to sell 20 million Switch 2 units in year 1, so that could mean that Nintendo will shift all of their production to Switch 2 pretty quick, we can't rule that out, if the demand for the Switch 2 is high, Nintendo may discontinue producing Switch units in favour of Switch 2 units pretty quickly.

I've posted something like this far more than 2 times. I predicted Switch would be the best selling system of all time in early 2018 (and there is a link to the thread in my signature). However, there are people who have come out every single year declaring that "this year would finally be the year that Switch sales fall off a cliff". Of course it never does fall off of a cliff. The cliff is never coming regardless of how much some people want it to come. Their reasons all sounded somewhat reasonable at the time, especially if the person really wanted them to be reasonable:

"Switch has already fired all of it's big guns and now it has nothing left."
"OK, actually this is the year where Switch has fired all of it's big guns. Now it really has nothing left."
"The Switch has no games."
"What people actually want is a system that plays all of the AAA third party games."
"Switch won't keep selling without a Pro model, because what people really want is a big system upgrade."
"The only reason Switch is selling well is because of COVID. Once lock downs end, then Switch sales are going to really plummet."
"This is the Switch's last big year, because next year Nintendo will release a successor and then Switch sales are over." (2021)
"The Switch can't sell forever." (2021)
"OK, now that COVID lockdowns are over, and it really has fired all of it's big guns, it has nothing left in the tank."
"This is the Switch's last big year, because next year Nintendo will release a successor and then Switch sales are over." (2022)
"The Switch can't sell forever." (2022)
"I'm not saying that Switch sales will fall off a cliff. I'm just saying that it's going to have a major sales downturn and it can't keep selling forever." (2023)
"Everyone already has a Switch. Who is left that is going to buy one?"
"Switch sold really well when Tears of the Kingdom released, but holiday sales are a lot lower than expected. Looks like the Switch is done."
"Switch has been on the market 7 years. They are going to announce a successor any day now, and then the Switch is through." (2024)
"The Switch can't sell forever." (2024)
"With the Switch 2 reveal it's officially the endgame now for the Switch." (2025)
"Lol sorry to burst your bubble but the cliff is coming, and very soon." (2025)

All of these things were said by people who thought they were being reasonable at the time. But the biggest problem with this reasoning is that it's very clearly wrong. A person who was actually being reasonable would say to themselves, "Switch sure is selling a lot better than I thought,  I wonder why that is?" And an unreasonable person would say, "that wasn't the year the Switch failed, but surely this is finally the year that it's over."

The reality is that we have a lot of consoles in gaming history that were the most successful of their generation, and all of them sold somewhat after their successor released. The system that was the worst at this is the DS, and the system that was the best at this was the PS2 (and we'll exclude the GameBoy, because that was a very special case). A reasonable estimate for how Switch will sell after Switch 2 releases would be significantly better than the DS, but not as good as the PS2.

Since you are predicting the Switch's tail end to be like the DS, you aren't being reasonable. You are either wishing the Switch will fail or you are just plain lazy. Currently you are falling into the category of people who have been predicting the Switch's inevitable fail and have been wrong for 8 years straight. You can do better.

Every console stops selling eventually, sometimes quickly, but it's important to note that that's not strictly "cliff theory".

The whole meme of "Switch sales will fall off a cliff" was not that Switch would someday come to a rapid halt, but specifically that its sales would collapse early or in the prime of its life; it started with "Switch sales will fall off a cliff in 2018" which then became "Switch sales will fall off a cliff in 2019" and so on and so forth.

Switch sales dropping off once its successor comes out isn't "cliff theory".

mmm... This seems incorrect. N64 sold 5.54 millions in Japan, not 4.54.

Are you sure you did not make an error in 1997, and changed "a 1" for "a 0" in the million units? It will explain the difference.

(Still... tha machine sold worse than originally expected in Japan, and US market "saved" the total numbers of N64. But when you post numbers to compare, you have to do an extra check, cause errors happen).

The figures are correct but Famitsu tracked less of the market in the mid to late nineties and back then they were also less accurate than they are now, so that's why there is a big discrepancy.