One likely response is to impose higher inheritance taxes. So long as they replaced less-fair taxes, that might make sense. They would probably encourage old people to spend their cash rather than salt it away. But governments should focus not on redistributing income but on generating more of it by reforming retirement and education.
Age should no longer determine the appropriate end of a working life. Mandatory retirement ages and pension rules that discourage people from working longer should go. Welfare should reflect the greater opportunities open to the higher-skilled. Pensions should become more progressive (ie, less generous to the rich). At the same time, this trend underlines the importance of increasing public investment in education at all stages of life, so that more people acquire the skills they need to thrive in the modern labour market. Today, many governments are understandably loth to spend money retraining older folk who are likely to retire soon. But if people can work for longer, that investment makes much more sense. Deadbeat 60-year-olds are unlikely to become computer scientists, but they could learn useful vocational skills, such as caring for the growing number of very old people.