A very interesting post from legal point of view. As rightly put by Prashant Mali, the google and facebook should also have a column for successor/beneficiaries in case of death and the death can be verified when the heirs submit a death certificate of that person. However, in case of digital currencies I think if a person is using services of an exchange/wallet and such exchange/wallet has the same facility then the bitcoins should also be transferred in the like manner. Only 3% of Indians get their will made and that too when they are in the last stages of life. Nobody forsee the death and would prepare his will being a lawyer even I haven't.
It has already been incorporated in the registration form of millibits at
https://millibits.in wherein the successor details are also been asked for by the exchange in the "Nomination Form" and in case of death the remaining balance of INR and bitcoin are transferred. The bitcoin are transferred to the person holding dead man key. You may look into it and understand more from webmaster of exchange.
