I can still import a wallet from at least 2012 and move the coins using the official client just like it was created yesterday.

edit: and obviously you can't remember that but if you encrypt your wallet you can save it to long term storages like Dropbox / differrent servers / medias / etc, what Satoshi would most likely be doing

Any one of those individual private keys could be imported into another wallet software application (e.g Electrum). Then the funds can be swept to a newer wallet that has a seed backup.

Private keys are just numbers. That has not changed since the beginning.

They're still supported by most if not all wallets.