Going by shipment numbers and calendar year:

2024 - 13 million
2025 - 6.5 milllon (expecting Switch 2 release in March)
2026 - 2.6 million
2027 - 0.4 million

~162 million in the end

As bullish as I am on the Switch, I don't see how its making it to 13 mil this year.

2024: 
Japan - 3mil
America - 3-4mil
Europe - 2.5-3mil
Other - 1-2mil
That gives us a range of between 9.5 - 12 mil

13M will be very tough. My guestimation for 2024 is 12.74M sold from Jan to Dec 2024. Japan has been putting in the work, showing up Europe sale lately.
Japan: 2.96M (-25%)
NA: 4.64M (~ -25%)
Europe: 3.33M (-25%)
Other: 1.81M

12.74M

I'm thinking 15% down in Japan YoY and 25% down in the rest of world.

Here is 2024 so far for Japan.

-15% is viable. Honestly we could even see -10%

I stuck with -25% just in case there aren't any big games for the latter half of the year. If there is a big game in the latter half I can easily see between -10% to -15%

I think 15% maybe too low given how there isn't a big game that we know of for the holiday while most other years we do have one. 

I'm not saying there won't be one, but for now we don't have a tangible idea as to how strong a holiday lineup we'll get so we should air on the side of caution 

15% is not happening, let alone 10%. While it has done surprisingly well in Japan the past several weeks it's not gonna be able to compete with how well it did last year from week 18 till 41 and the successor will get announced at some point this year which will have a negative impact on sales including during the holiday season. 

Well of course it wont be able to compete with last year. We are on a down hill slope and so far this down hill slope has a very low gradient. We are essentially in uncharted territory for Nintendo that hasn't been seen since the NES. We are over 1/3rd of the way through the year and we are at -6.4% in comparison to 2023 sales. That looks very competitive but 2023 will be on top always from here on out. 2023 sold 3,949,463 units in Japan. The best selling week in 2023 was the first week of January (huge discounts) at 137,033 followed by the last week of April (pre-ToTK hype). There are 37 weeks left for 2023 and sold an average of ~79,988 units per week from next week to the end of 2023. Switch wont be able to sell an ~79,988 units per week but it can easily reach ~67,353 units on average from here on out leading to a total of 3.36M (-15%) by the end of 2024.

If we had a -25% drop in 2024, the Switch in Japan would sell 2.96M units. Meaning it has to only sell ~56,679 units on average per week from here on out.

I both scenarios are very likely. 56k may seem too low and too easy for the Switch in Japan, but I definitely see it as a hard floor for the rest of the year.

The point I'm making is it did so well during those weeks last year that there's no way it's gonna be able to keep up enough to only be 10-15% down by the end of the year. How can it easily reach that amount on average for the rest of the year when it's sold less than that 12 out of the 15 weeks so far? There's nothing massive happening like the Mario film and TOTK releasing close together to boost sales for a few months like what happened last year. The 25% drop scenario is realistic though I wouldn't say it's a hard floor since reaching 3m will be tough.

Yeah it did amazing last year which is why it was able to sell 3.95M in Japan alone and this year wont be able to match the 80k weeks it had in the summer (with a few +100k too). This year is still on the seesaw between good, bad, and meh.

First, if we want to understand how well the Switch will sell in Japan, it would be amazing if we can see how many purchased units go over seas. Because obviously they are being sent to other countries, Japan is at like 1 in 3 people have a Switch almost (rough estimate). China? India? maybe? Because that is one of the reasons it is still selling well in Japan, also because the yen has depreciated a lot in the past year. Meaning other countries money is worth more in Japan making items seem cheap.

Second, we need to understand what sells best in Japan. Monster Hunter, Shin Megami Tensei, Disgaea and Thousand Year Door. Those will keep the Switch alive and over 56k for the summer at the bare minimum. And then we have the holiday games which we'll learn about in the next Nintendo Direct. When do we think itll be? May?

I do agree -25% is realistic. I'm just setting another expectation for it since the YoY is still very close. Honestly it is very competitive to 2018 sales. ShadowLink93 has an amazing chart and 2024 actually ahead of 2018 in sales. Though the holiday is where 2024 will fail and 2018 will surpass. Like wow 2018 holiday sales were crazy, 100-300k each week, wow.