The Delta SkyMiles Program Rules do not exactly specify what happens upon death of a member. The rules do however state that “miles are not the property of any member. Except as specifically authorized or otherwise in writing by an officer of Delta, miles may not be transferred under any circumstances, including, without limitation, by operation of law, upon death, or in connection with any domestic relations dispute and/or legal proceeding.”
This language leads me to believe that officers of Delta do allow Delta SkyMiles transfers to beneficiaries in the event of death. At least I would hope they do.