SD cards are a simple serial interface that is well-documented at the block-device layer; the filesystem will likely be some variant of FAT, and I doubt the JPEG standard will be entirely forgotten, so while hardware like SD card readers may not be produced commercially anymore by then, anyone with the right knowledge can still make one.

This is, of course, supposing that the rather scary situation of heavily-locked-down devices and completely-restricted access to knowledge has not occurred...

> To computer enthusiasts with legacy hardware/software maybe.

All you need is one person that can access it. Do you know of any technology that we can no longer access?

They are lots of great stories about the hard work people had to do to access them (the video scans of the moon for example) but none that I know of that failed.

> All you need is one person that can access it. Do you know of any technology that we can no longer access?

Technically, that's true. However, would it be economically feasible for the average person with ordinary family photos?

Fwiw, a properly fixed, permawashed, and archival washed silver gelatin fiber print should outlast our grandchildren.