Nope, this is no existential question (although...). Everybody's talking about "When will Bitcoin die", but what if you die, and your family don't find your key, or don't understand it, or think it's only a useless sheet of paper with some code on it, or simply throw it away... Does this mean the currency's gone forever?
I find the possibility of this event rather realistic (yup I don't believe in eternal life), so that means that someday there might be 21M BTC but only 18M (and counting down...) is left in the market?
Yeah, it's gone forever, lost coins.
If you are saving bitcoins for your loved ones then you should clearly explain to them how bitcoin works and how to inherit coins in case you die.
The simplest form of bitcoin inheritance is writing down the private keys on a piece of paper and storing it in a safety deposit box.
You can use bitcoin protocol for inheritance, but these are a bit technical and complicated, contract/time-locked transaction.
https://en.bitcoin.it/wiki/Contracts#Example_4%3a_Using_external_statehttps://en.bitcoin.it/wiki/TimelockShamir's Secret Sharing Scheme -
https://en.m.wikipedia.org/wiki/Shamir%27s_Secret_SharingThird-party services. Currently Coinbase doesn't allow to add a beneficiary, but through will and testament ownership of Coinbase account can be transferred.
https://support.coinbase.com/customer/en/portal/articles/2321225-how-do-i-gain-access-to-a-deceased-family-member-s-coinbase-account-I guess in future there would be more bitcoin/crypto/digital inheritance services.