Of course, I assume the current president will preside over the event. I was only speaking about past living presidents.
The saddest thing I heard was in an interview with Nancy some years ago, when he was in the moderate stage of the disease.
She said someone presented President Reagan with a model of the White House. He graciously thanked the person, then later said to Nancy; "I know this building has some connection to me, but I don't remember what it is."