The drives to read them (Blu-rays) will be the problem. Pioneer stopped manufacturing them in 2024, only LG drives are available now.
Coincidentally I just bought one, they’ve doubled in price now recently.
Also bought some M-Discs to try. They’re half the price in Japan (Amazon) compared to Germany.
If I’m not mistaken only optics are really unique to BD and need dedicated production? Everything else is rather universal components so even a hobbyist should be able to build a BD reader from scratch - having access to servos, cnc, and 2000s-level electronics?
In a 1000 years even if they don’t have the drives, as long as they still know roughly how it works maybe they will photograph it with a microscope and read the tracks in the M-Disc from that. Then they will have to decode it also of course.