I hate the argument that Mankind/Taker HIAC was just "a spectacle" and not a match. I understand it, sure, but it's a BS take when you consider that the WWF was always about spectacle over technical excellence. What made Foley so special was that he could do the violent crap in such a way that it told a story.
If HIAC doesn't happen, then we still get Mankind/Taker with another stipulation that allows Foely to take a sick bump. Maybe he gets chokeslammed off the top to the floor, maybe a toss off the stage, whatever.
Health-wise? He's still retiring around when he does, maybe holding out until SummerSlam 2000 at the most.