I think copyright is inherited by the heirs (in most cases relatives of the deceased) and carries on quite a long time after death. So the relatives may actually sue you, and any discussion WRT relicensing would have to be addressed to them.

I actually consider putting something into my will that states that all my open-source contributions are relicensed to "public domain" (CC0 [1]) once I die.

[1] https://creativecommons.org/share-your-work/public-domain/cc...

Its also possible to transfer your copyrights before your death. For example to the FSF or to Software Freedom Conservancy. I hear there are tax implications for copyright bequeathment, which is why transferring copyrights is preferred.

https://sfconservancy.org/copyleft-compliance/

Their heirs could do precisely that.

Yep. It’s how the Marvin Gaye lawsuits these past few years have been able to happen (despite him being dead). His estate is suing.

IANAL but I believe a Qui Tam could take place by surviving family. Or inherited copyrights, etc.

Inheritance exists.