I know it's stressful for Mom to look forward to being a "caretaker," when they've been independent for a number of years. Their retirement community in Florida has facilities for residents who "go dotty," as they say down there, but I hope things will work out so Dad can be near us, if his condition deteriorates quickly. He might have a number of years while he still has pretty good functioning; we'll just have to wait and see.
I wanted to keep pretending it was just ordinary forgetfulness, but Mom wouldn't let me.
I can sympathize. My former FIL was quite elderly when he began to confuse my children with his and to confuse me with my late MIL.
I tried to alert my in-laws (I was an out-law), but they were in complete denial.
He was a terror to drive with, but the "real" children wouldn't take that independance away from him until he very nearly killed me and my newborn in NJ. I declared I would never drive with him again and earned the wrath of all.
The daughters thought he only needed someone to check in on the weekend, conveniently when they were down for the weekend, They wouldn't listen to me or the other "outlaw" who took care of him. He wouldn't take his meds, he lost control of his bowels, he was like child in temperament.
It was Hell since his wife was long gone.
Since they're in Florida, it may be a good idea to learn as much as you can about the end-of-life issues down there. While you have plenty of time - so you can be aware.
It's always good to be aware.