I don't see anything about death of a client being a release of the privilege:
C. A lawyer may reveal:
1. Confidences or secrets with the consent of the client or clients affected, but only after a full disclosure to them.
2. Confidences or secrets when permitted under Disciplinary Rules or required by law or court order.
3. The intention of a client to commit a crime and the information necessary to prevent the crime.
4. Confidences or secrets necessary to establish or collect the lawyer's fee or to defend the lawyer or his or her employees or associates against an accusation of wrongful conduct.
5. Confidences or secrets to the extent implicit in withdrawing a written or oral opinion or representation previously given by the lawyer and believed by the lawyer still to be relied upon by a third person where the lawyer has discovered that the opinion or representation was based on materially inaccurate information or is being used to further a crime or fraud.
http://www.law.cornell.edu/ethics/ny/code/NY_CODE.HTM#4-101(a)