Re: Future readability...
"This physical format has been commercially available since 1982. Yes, 33 years. An eternity in technology. Whenever the format has been upgraded the physical form remained the same and any new readers are compatible with all previous formats sharing this shape. I see little reason for any future passive storage media to break this long continuity and change to a different form factor."
The polyvinyl chloride disc has been commercially available since 1931. Yes. 84 years. An eternity in technology.
However, there were no widely accepted material, size, speed or format standards until the 1950s. Anything pre the microgroove and vinyl era will not play back on any of today's turntables, which are now themselves also effectively specialist audio equipment. The era of that technology's material, size, speeds, format, wide acceptance and use lasted effectively from mid-1950s until mid 1980s. About 30 years. That format, material, disc sizes and speeds are incompatible with any widely used current (and probably future) technology.
I see little reason to expect optical standards to remain backwards compatible if a better medium, format, size provides the market and profit for the propagators, and also offers must have advantages to consumers (price, capacity, longevity, speed).
Your optimism about standards is enormously misplaced. The likes of Sony, Apple, Phillips etc. would create a new proprietary standard at the drop of a hat. Backwards compatibility just does not factor into the mindset of these profit seeking vultures.