A question about the abolition of Medicare

It just occurred to me a minute ago: how is dumping the cost of people's healthcare in their golden years onto the private insurers going to affect the rates? I mean, right now Medicare pays all or most of the cost of taking care of the vast majority of senior citizens, which no doubt has a very positive effect of the bottom line for insurance companies and lets them charge much lower rates. What happens when they start getting customers that they will have to take care of until death?