Edit: To clarify:
Is it even possible, financially speaking, to keep adding storage? I mean, advertisements don’t even make a lot of money, is the indefinite growth of server storage even sustainable?
Or will they do what Twitch does with old content and just delete them?
Google has said they’ll start deleting long inactive accounts. I’m guessing they’ll go for unlisted next. Eventually they’ll try and prune their catalog to not have tons of unprofitable videos.