Well, it's a complicated matter, isn't it? Weekly sales of the PS5 are healthy now so that's a good sign. On the other hand software is still nowhere to be found in the charts, so it looks like this is still launch demand. We have to keep in mind the PS5 is at 422k lifetime sales right now. The Wii U had sold that after two weeks. The 3DS was at almost 600k after two weeks. The PS4 was at 500k after two months. (I'm using the VGChartz comparison tool so I hope these numbers are accurate).
I certainly wouldn't say there is a "brand crisis" in Japan for Playstation consoles, but Sony's market is shrinking (even though I'm sure not many people expect the PS5 to sell as bad as the Wii U). Even if we expect the PS5 to sell 10 million units lifetime, that's still a drop of almost 6 million units compared to the PS4 + Vita install base. The question remains: Is the current level of hardware and software sales enough to attract a large amount of Japanese third party support? And will the console sell better or worse than PS4? Because Playstation consoles (in contrast to Nintendo hardware) have actually needed good third party support in the past to sell well in Japan. If the install base is not big enough more third parties could release their games on Nintendo consoles, which would result in lower hardware sales for the PS5. We'll have to wait and see what happens.
But that's just it, its quite simple in that we're looking at system which hasn't been well stocked. Not much more can be said beyond that (it also has a carry on effect for software). Not so different from the PS4 but instead of delaying the launch like PS4, Sony simply gave Japan crumbs from a "global launch". But there was a fair amount of doom and gloom based on pre-february numbers whereas those numbers meant very little and we really won't see what the demand is til later in the year.
Regarding software, for as long as places outside Japan still see playstation carry the majority or just a high portion of sales for many titles (Persona Strikers for example), I don't think sony has too much to worry about in terms of loosing support (Until Switch 2 at least). As far as more niche/Japanese local hits, I think its a given that Playstation has lost 90% of exclusivity there but those aren't normally the system sellers.