Good topic this. I've recently been thinking about that myself. I think I'll be printing out a paper armoury backup and keeping it in a safe for my kids in the future!!
This definitely will become more and more relevant these days.
Even outside of BTC, this is something that people are doing in the age of the internet and social media. Many wills now suggest that you should put access to somewhere where they can your login and password for all of your social media sites, BTC wallets, etc. so that someone can manage your 'online identity'.