It's an intangible, asset, not really "owned" like a dining room set or an oriental rug or a classic car or even a house, so it would be tricky if you haven't left your dn account access information to anyone other than yourself, after death, I'd imagine.
It would be interesting to know if legal documents such as a will could cover the transference of domain names in an inheritance setting, but the caveat likely be related to whether the domain is still actively registered under your own name, ie, not dropped and re-registered by someone else.