Aside from scratch, finding device to read/play it shouldn't be hard since you could use any DVD/BD reader. I expect few company will continue to make DVD/BD reader in the future.
CDs, DVDs, and Blu-rays will suffer the same fate as cassette tapes. They will become obsolete. Modern laptops are already sold without such optical media. So, in the future, you'll have to buy a separate device just to run the discs. Compared to that, USB ports are much more represented and used for all kinds of things (at least for now).
You're right, although i don't think it'll be obsolete that soon when bluray is still somewhat popular.
I am confused by the stated service life of the device of 200 years. About CD also claimed that data on them could be stored for up to 60 years, but as practice has shown, after a couple of years the data became unreadable. Even if the creators of Blaustahl USB made a 10-fold mistake, the device’s service life will still be an impressive 20 years. By then, technology will surely advance and more advanced devices will appear.
Such claim is only true if you buy ones which meant for long-term storage and you handle it very properly. Although i recall many of my CD lasts longer than 2 years.