Arrogant fools in every age think everything is better than everything that preceeded it.
How about we print out everything at least once, photograph it in black and white? That lasts a long, long time...
Of course, I'm one of those people with old computers stashed in the closet because of various treasures on them which will probably never be accessed again....
Lots of stuff will get lost, but that is nothing new. The thing that makes digital special is that files can be copied to new media without loss. Nothing guarantees that they will be.
And even if family images could be preserved forever, who will have the time to view them. In the past five years my family (four adults now) has accumulated about 50,000 images. All but maybe a thousand are either trash or redundant.
When my daughter got married I spent several months putting together a digital slide show. I went through 25 years of old photos, scanning the best, cropping them, and correcting the color of faded prints. I wound up with about 700 images worth preserving, all of which fit on one CD.
Will those survive a hundred years? They will if there are people interested in keeping them.