What could change the global savings-investment equilibrium?

One of the causes of the very low level of long-term interest rates is the rise in the global savings rate, which shows a situation ( ex ante ) of excess savings over investment. For long-term interest rates to rise sharply, which would trigger a debt crisis and a sharp fall in asset prices, the excess global savings would have to disappear. Is this possible? Population ageing normally reduces savings; but this has not happened in Japan and there may be an inheritance motive; The transformation of the global economy into a service economy ought to reduce investment needs; but new investment needs will appear due to the energy transition. So there are several uncertainties; it would be very useful to know how long the situation of excess global savings will continue.