Hopefully Newman has at least 10-15 years more left in him. I don't think he is that old yet, he isn't even in his 70s. His father died at 69, but he was a heavy smoker and died of lung cancer, that's a bit different I think. His mother lived until her mid 80s, which is probably a much better estimation of how long Newman will still be with us.
Alfred probably would've had another ten or so years of life if he hadn't died relatively early. Oh well. Some people pick up bad habits. At least he was still going strong at the end. 'Airport' is a fantastic score.
As you said, hopefully Thomas outlives his father by a decade or more and continues scoring films to the end, just as his father did.
