So to preserve digital movies we should carve out all of the data in stone. That seems completely feasible.
It is not feasible of course for every information we currently have. I just pointed out that if digital storage is done well, it is by far superior to film (assuming good resolution of digital encoding). Even on hard drives or optical discs it is still better than on film, as you are not losing the information over time like on film. You just need to replace hard drives or optical discs every now and then and have a backup system.