Spooky, they don't say because they can't...not right now, anyway. They are pretty good at being able to tell that a person is going to pass within 12-24 hours, but there may be days--or even weeks--prior to that time that he may seem to rally, especially since he's off medications which may have been toxic to him. They will give him pain meds, though. Watch the urine bag carefully (I assume he has a catheter.) If the urine turns very dark, you will know the time is getting very close. Also when he stops talking and refuses anything except a few sips of water or ice chips. The hallucinations can also be a signal, especially if he sees family members who have passed.
I know this is a rough time for your family and I hope it will not drag on much longer.
Hugs,
Connie