The Queen may well outlive them. Has anyone considered the possibility that Camilla is ill? She is a heavy smoker. It would explain the announcement and the speed with which the ceremony is to be performed.
You raise an interesting point. Last Cindy Adams wrote in her column in the New York Post that Camilla was battling cancer after being a heavy smoker for many years. Then nothing further was reported. I don't know what happened to that story.