You can find the answer in the Help Centre (make sure you are signed in first if you are using FamilySearch.org). I search for Deceased Member and get 2 helpful knowledge documents (remember you can search just by the number):
1. 1025085 which is from A User’s Guide to the New FamilySearch Website (20 February 2012) (LDS Version) Handling Ordinances That Were Reserved by a Member Who Is Now Deceased or Incapacitated
If a Church member reserved ordinances and then dies or cannot complete the ordinances for other reasons, those ordinances remain in their current state unless someone else has the cards and finishes the ordinances. If cards were never printed or if the cards have been lost, you need to work with a system administrator to see what can be done.
Currently, system administrators cannot change all of a deceased member’s ordinance reservations at once. Therefore, please limit your request to ten individuals at a time. Your request can include more individuals if they are in the same family.
Please send the following information to firstname.lastname@example.org:
The person identifier of the individual whose ordinances need to be unreserved.
The name and death date of the deceased individual who reserved the ordinances.
Your relationship to the individual who reserved the ordinances.
Your full name.
Your birth date.
Your helper access number (which you can find in your user profile).
If the individual who originally reserved the ordinances is not deceased but is no longer able to print cards or perform temple work, please explain the circumstances.
This knowledge document then has links to other related topics
2. 103836 How long does it take Church membership to transfer deceased Church members’ information to the new FamilySearch?
The Church Membership Department has to be notified of the deceased member’s death date. The time period for Church membership to transfer a deceased Church member’s information to the new FamilySearch may take up to a year from the date the Church Membership Department receives the information.
Personal comment: when a friend passed away and I was helping the family retrieve all the names from his reserve list, the ward clerk sent in the notice of death and within days the account was closed!
Remember that previously printed temple cards remain valid.