Interesting that he completed all but one design on both WISC and WAIS, since the WAIS is intended for noticeably older (and presumably more capable) examinees. So no, he didn't hit the absolute ceiling, but yes, he did not meet discontinuation criteria. And, of course, 19 is the max scaled score. You should definitely obtain raw scores for any subtest with a 19 scaled score, if you want to be able to calculate extended scores in the future.

As to the wild ride--yes and no. There is no way to prepare for it, nor is there a way to predict what form it may or may not take. As with any child, of whatever intelligence classification, we parent the child who is in front of us right now. With long term principles, yes (character, virtues, self-management, responsibility, etc.), but beyond that? Part of the beauty and the mystery of raising a human being is that we discover along with them how their paths unfold.

Enjoy, treasure, love. That's enough.

...pronounced like the long vowel and first letter of the alphabet...