Just a reminder that Playstation 3 launched on November 11th, 2006, it had pricing similar to what we expect from Playstation 5. Which were ¥49,980 / ¥59,980 depending on the SKU. 

Launching with 88K sales, by the end of 2006 PS3 managed 466K sales in Japan. 

I honestly don't think Sony needs to ship more than 500K in Japan for 2020 and the first week of 2021. If the pricing is closer to ¥60,000 than they probably don't even need to ship 400K to Japan. So overall the vast majority of what they are going to manufacture will end up elsewhere. At this point I'm wondering if PS4 and PS5 combined will be able to sell 1M this year in Japan...