Post-replacement legs will be the crucial factor. The DS and 3DS each sold around 9 million units post-replacement. On the other hand, PS4 only sold around 3 million.

Nintendo's forecast puts them at just under 155 million by the end of this FY, but reaching that mark in practise will be challenging and they don't seem to be pushing hard to make it happen, so to be conservative, let's say they sell 11 million and end up at 152m as of March 2025.

If the successor is expensive, say $450-$500, then the Switch, particularly the Lite, could see a second life next gen as a budget alternative, at least until the Switch 2 Lite arrives, which took 2.5 years with the current Switch.

That could be enough to climb passed 160m.

On the other hand, there is the possibility that Nintendo does a Sony and quickly kills off the Switch in order to shift production capacity and players to the successor as quickly as possible.

The Switch clearly has the potential to top the PS2, it just remains to be seen if Nintendo will let it live long enough for that to happen.

162M? Geez, it seems like the potencial maximum number for the PS2 increases every time this topic is brought up. I thought the maximun possible number for the PS2 was 160.9M something like that

Even if the Switch ends up in the gray area between 155 and 160M (or 162M as RolStoppable said) and we never know who sold more, the Switch or the PS2, me personally, I'll declare the Switch the "winner", the most sold console. Sony is the one to blame for not having given us clear data about PS2's final shipment. I think that you can't just have the console sold, you have to provide clear data about it. In circustances of uncertainty, better stick with proved information. As for recording the "The most sold console ever" in websites and such, I defend something like "The Switch is the most sold console ever" and a disclaimer at the end.

Of course if the Switch manages to land on this area. It can go beyone 160M or fall short from 155M for whatever reason. I'm just advancing a conversation that might happen in the future

The calculated range is 158.6m to 161.8m and there's no maths that could push it any higher. That's why 162.0m will constitute absolute certainty that Switch is the best-selling system of all time while 161.9m could still have people argue about rounding.

The thing is that every year we've had people worrying about Switch hitting a certain threshold in lifetime sales. Even despite starting in a healthier position than the 3DS, it was still in doubt for a lot of people that Switch could sell more than 75 million units. Every year the bar had to be moved higher while the doubters tried their best to lay the bar as low as possible. In early 2020 we still had people questioning if 100m is possible. Then we went from 110m to 120m to 130m to 140m to 150m to now 160m.

It was always a question of longevity, but rarely did it happen that people actually focused on Switch itself, and instead they tried to draw parallels with other systems and repurpose those analyses back to Switch. What Switch has going for it is first party support that is A+ and third party support that is B+. It's only B+ because megahits like Monster Hunter are extremely rare to be made, but the number of potential million sellers and overall number of quality additions to the library are very high. A steady flow of interesting content is what makes a system sell for a long time and there's still no end in sight for Switch, because we are still getting a new first party game almost every month and a sequel to Pokémon Legends is announced for 2025. Third parties aren't going to stop supporting Switch anytime soon anyway, because their own transitional periods from current gen to next gen keep getting longer with each generation.

Switch is guaranteed to hit 150m before its successor launches. We also know that Switch's successor won't be cheap, so Switch will continue to sell alongside its successor for a couple of years. Perhaps with fewer first party titles that the 3DS got post-replacement, but for sure with more third party games. The 3DS entered its post-replacement phase on the back of a 7m fiscal year whereas Switch will have at least 11m in the same situation, so it's undeniable that Switch will go into its final phase of life with much better momentum. Adding 10m more after the fiscal year ending March 2025 isn't that big of a challenge under these circumstances, especially because it's possible that the successor won't even launch during the first half of calendar year 2025, which would allow Switch to hit 155m before getting replaced.

Half a year ago I said in a different thread that Switch's chances to outsell the PS2 are at 90%. Nothing extraordinary has happened since then, so the odds remain the same. I acknowledge that there's still a realistic possibility for pessimistic scenarios to come true, but at the same time the likelihood for them to happen is very low. The requirement for Switch to fall short of the PS2 is pretty much a repeat of the DS to 3DS transition where the successor system was messed up and got its price quickly cut to shift sales from the old system to the new system. But such a collosal blunder is improbable because of how Nintendo is handling the Switch platform up till now: It's carefully and patiently planned as opposed to the DS to 3DS transition where Nintendo had rushed the successor to the market.