I think PS5 still has the potential to outsell the PS4 in Japan if Sony get their shit together. This will probably be their longest generation and there are the possibilities of VR exploding in popularity (worldwide.. but it could extend to Japan to a degree) and a handheld model (unlikely but not impossible).
As bleak as things look right now for Playstation, Japan still ranked 3rd behind the UK and ahead of Germany in "PS5 Active Console Volume" as of last March. And without more information on digital ratios, physical charts don't portray the full picture. PS5 should sell anywhere between 7-15 million in Japan. Anything lower would be Sony's fault, or the result of a shockingly short generation.
In case you guys missed it, it's now being reported than Sony will produce 30.5 million PS5's in FY 2023. That's an insane number but it should be enough to meet demand in the majority of countries. I expect the PS5 revision (reported to launch late 2023) to coincide a pricecut.
That is insane and there is no way a premium priced home console could ever sell that much in one year. The reason DS could do those numbers was partly because it was a relatively cheap handheld at the right time before mobile took off. Also DS could sell 7 to 8 million in Japan and the maximum that the PS5 could sell in one year in Japan would be 2 million which means it needs to sell 28 million outside of Japan to reach 30 million.