I imagine that in the future what will happen is that when a child is born, their stem cells (possibly from the umbilical cord) will be cryogenetically preserved and will form a reservoir from which medical interventions can be prepared as much as 50 years later.

Of course, this assumes we will put a new premium on human life not just limited to the children of the privileged few, which in turn presumes some kind of limitation on human reproduction (steady state population in which births == deaths). Implies a high degree of rationality - who gets to reproduce, and who doesn't? It would take a lot of energy to preserve all those stem cells, after all, and energy supplies really are limited.