I believe that 40 years or so a call to free lost coins will begin.
Any address that has not had a withdrawal in 40 years will be listed as an abandoned account and have 1 year or 2 years to do a withdrawal. It will will then forfeit and go back to the fund of coins left to mine.
LN (and other layer 2 protocols) will make it less necessary, and less common for particular outputs to be spent.
If you have a sufficient number of channels, and if your counterparties are cooperating, you may never need to close your channels because you can just rebalance your various channels.
Further, there are always security risks associated with accessing your private keys and spending your coin, so individuals should generally not spend their coin unless they need to.
Sure, Bitcoin is code, but how would Bitcoin know that you're dead?
It can't. Period.
If someone wants to, they could create a nLockTime transaction that is valid a very long time in the future, that is intended to be sent to an address created for their next-of-kin. This is ultimately something that the owner of any coin should decide.
I would point out that some wealthy people choose to not give any money to their heirs.