Was the tree installed too deep, or was the grade changed after installation?
I guess that management all boils down to how deeply attached the homeowner is to this particular tree, and how much effort and resources they're willing to expend to retain it. If it's a tree with deep sentimental value to the property owner, they might want to consider correcting the grade, fungicide applications, and parhaps guying the tree, to slow its decline and hedge their bets in the event of a failure.
Perhaps they should also consider collecting and germinating acorns from that tree, in order to continue its legacy.