1. The end of Sony standalone players (in Japan) isn't necessarily the end of the bluray format. There are other manufacturers.
2. However, it is concerning that Sony, the creator of the format, is moving away from it. If the PS6 does away with the disc drive, that's complete abandonment. It's possible Sony plans to implement a high quality streaming service to replace physical media, but not guaranteed.
3. 4K Bluray likely struggles because it's not a huge upgrade over 4K streaming or even 1080P for the average user who watches on a small screen. A majority of users prefer convenience.
4. Given that Video/Audio-philes are a niche market, we may see a contraction of what is available due to tariff barriers. Some low-demand products are only viable if one manufacturing location can amortize its costs across the entire global market. If trade barriers are put up, that market shrinks and becomes less efficient. Products that were barely profitable become unprofitable. No U.S. manufacturer will on-shore production of such products because the U.S. market isn't big enough to make them viable. That may have contributed here.
5. There is nothing to prevent high quality audio/videophile oriented streaming services from picking up the slack, but we can probably expect them to be expensive and openly hostile to the concept of ownership. The joy of finding a title you've been looking for in the bargain bin at a local store could become a thing of the past. Sony probably views a 4K Bluray discounted to under $5 as a lost opportunity.