And what is PS5 going to do?
Hopefully for Sony sell better in Japan than the PS4 did, especially early on as the PS4's start in Japan was pretty much a disaster, being outsold by the Dreamcast and Wii U of all things in the same timeframe (first 6 or 9 month, can't remember which one)
PS4 is on it's way out, selling way less than 10k with such a big release is a pretty sad sight, especially since the PS5 is at least one year away.
I can only see PS5 doing worse in Japan than PS4. Think back to 2013. If a Japanese person wanted a home console, then what were they going to get? Wii U sucked (and had a small library) and Japan never buys XBox. That just leaves PS4. It was the only viable option.
This time around Switch is a viable option. Most weeks, when we see the top 30 chart for Japan, there are several games that get both a PS4 and Switch version. Switch is now a viable option. It is reasonable to expect that after PS5 releases, a lot of Japanese games will be PS5 and Switch or possibly Switch only. Switch has already outsold PS4's 6 year total in about 2.5 years. Switch is definitely the main platform for Japan. There are going to be a lot of Japanese PS4 owners that will just buy a Switch and never consider the PS5.
In Japan PS5 is definitely going to decline compared to PS4.