Earlier quoted context omitted.
If he didn't have a backup plan in place to be accessible by his estate, then yes, the coins are dead. The coins dying with him are actually the best case scenario for all other holders. "Lost coins only make everyone else's coins worth slightly more. Think of it as a donation to everyone." - Satoshi Nakamoto
Unless this alerts people to the risk of losing a private key and they decide owning Bitcoin isn't a great place to store wealth.
You can even split up your key in an M of N format so that a) no single compromised location causes loss, and b) some number of storage locations can be lost without losing your key.
Can you do that with gold? Land? Art? Cash? Bonds? Stocks? All of these rely on either securing a single location where the wealth is stored and moving to another place is either expensive, risky, or necessarily impossible (land/buildings), and/or they rely on trusting some custodian to preserve your claim on that wealth.