If this happens, I think nothing should happen to the wallets of these people, consider lost and the total of available coins will decrease. I do not think it's fair since somebody can get this wallet even if it's 10 years later. The idea I saw after some time erasing those coins for me does not make sense.
Yes, I guess, this thing will happen if this is the case or situation and this should happen that the coins will remain on his wallet and be stock on and since it is stock on the demand of bitcoin increases because his coin is not moving.
but if he life the key to his children then they will distribute the bitcoin according to the law. and i am sure that if a person has so many bitcoin in his wallet he will certainly store his wallet key some where in a safe placer where only his children can only reach after his death. so the total number of bitcoins are not going to decrease.