TOTK and BOTW really turned the series around in the region.

I agree it is very odd. My local Target has had one PS4 sitting on its shelves for months. Unless it keeps on selling then they put exactly one PS4 out. 

Think there is definite China effect on Japan numbers, we have multiple reports of Japanese shops being flooded by Chinese exporters. The question I couldn't really figure out was why now, but apparently the Chinese government did something like not approve any foreign games in the market for like 8+ months recently ... that likely spooked Chinese buyers into wanting Japanese PS5/Switch/even PS4s.

If I was Chinese I wouldn't want a Chinese Switch or PS5 or PS4 either ... imagine you're looking forward to a game and then the government on a whim just decides "well we're not approving any games for Chinese market release for the next X number of months". Or even just flat out not approving certain titles at all (Animal Crossing, Call of Duty, GTA, and several other big games are not approved for release in China). It's easy to import a Japanese system and games.

If Switch 2 stumbles out of the gate and doesn't establish itself like many of us expect, then that changes the conversation.  Otherwise, it's highly unlikely in my opinion.

Switch 2 has very little impact on the PS5 as they serve different markets. What will impact it is if China does anything to stop the flood of 'gray market' imports of Japanese consoles into China, as the Chinese government loves to have full oversight and control and these gray market imports skirt around that oversight and control. I would not be surprised if China cracks down hard on the gray market in the near future.

Which is also another reason why if you're a gamer in China, you'd want to hurry and get a Japanese Switch or PS5 now. Though I think the Chinese government is kind of content to look the other way on a lot of gray markets there. 

Anywhere else in the world I would agree with you, but this is Japan.  Chances are that Switch 2 will be capable enough that it will satisfy the wide majority of people in the region and if that happens, I don't think the PS5 will be able to keep up good numbers against it.

If you only take the time frame from beginnend of May until now (cw17 - cw28), the Switch had his best sales of her life time, at 1.05 Million units.
2nd best year was 2021 with below 1 million units sold.
That is crazy.

I don't see how the Switch 2 will cause enough of an impact since the PS5 will have sold 5-6m by the time it comes out and I can't see how it doesn't do another few million afterwards.

Even with a conservative 4.6m LTD by the end of this year an average of just 1m for the next 5 years is enough to beat the PS4 which seems easy unless the PS6 is a 2027 release.

Well the PS5 needs to outsell the PS4 by more than 3 million to pass the Wii. I don't think it can do that. The PS5 should be at its peak right now, but demand hasn't increased as much. I don't think any future software will drastically change the demand either. The only possibility is that the demand in China sees an increase and more units are sold to the grey market. It might outsell the PS4, but the 3 million difference seems very far away. 
Oh maybe you're only talking about PS5 selling more than the PS4.