you would let whomever you want to have or manage your observations know what you want to happen. if you want to put all your stuff into the public domain, you should give your passwords to your executor with instructions on setting your licensing to CC0. if you want to give copyrights to a specific person, you can do that in your will or else it will go through the default probate process. i doubt iNat will want to manage copyrights for a bunch of photos even if you want to give them your photos. furthermore, i would guess that if there is actual monetary value in your photos, that the real value lies in the source images outside of the system anyway. so if you want to gift that value to iNat, you’d probably still want someone to market your images and then send the proceeds to iNat.
i’m not sure how what you’re describing here is better or how it is effectively any different than giving someone your password once you’re gone. i also don’t see how it would benefit a small organization like iNat to try to set up a costly process to determine that someone died and to transfer access to a designated person upon death (or take some other action upon death).
iNat staff have made small tributes in the past to folks they knew personally, but that’s not a standard process.
there are several previous threads that may be worth looking through, such as: https://forum.inaturalist.org/t/personal-statement-in-profile-does-it-weight/44989/6.