Ive has done some very good things, however he is not the be-all end-all designer. There are a lot of amazing contemporary designers and in my opinion, many better. Apple systems have stagnated a bit in general design and overall look for a while now. Do I think he should go? No. Would I be crushed if he did? No. He could move on as a designer and some young, fresh, new talent could pick up and move on... most likely for the better.
Cook is the only real potential successor, so all of these Ive comments are rubbish on that front. It would never happen.
People's priorities change, money isn't an answer always. I'm at the same point myself in my professional career. I have 15 years in a demanding but well-paying field, the money no longer matters and it isn't my motivator. I can go do something I enjoy for a fraction of the money where I want to live and drop 90-100+ hour weeks.