This is what will eventually happen. Sooner or later all crypto funds will be lost/inaccessible - given enough time. If he had kept his funds in stocks or just a plain old bankaccount (or even gold), you would have now had access to the funds.
The lesson here - if you are about to die, sell your crypto...
If they kept the credentials to access the wallet then it will not become one of the many lost coins, also why would we choose gold or stocks? Does it give a 900% return in just a year? I don't think so, not even in the lifetime of your son or daughter will banks, stocks or gold will be able to replicate what bitcoin has done in a decade.