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?
I think the most intelligent thing to do is have everything of your bitcoins documented and kept in secret so that when the time comes, you can just give them, your family, the rights and the claims to your bitcoins. You can also entrust the bitcoins to a certain company to keep it circulating.