It is difficult to say exactly what lies on the horizon but one thing is sure: we already have rationing of health care, not just for seniors but for everybody. The rationing is financially based. If you do not have insurance you get whatever the public system will allow before they cut you off and send you home. If you need a drug that costs $2000 a month you will not get it unless you can find a nonprofit that will pay for it. If you do have insurance your treatment is limited by what the insurer will pay for and where you have to go to get it. Many insurance companies still claim that bone marrow transplants as a treatment for leukemia are experimental and thus are not covered. Any oncologist will tell you that this is a treatment method with proven effectiveness.
If you have very good insurance (or a great deal of money) you may get your cancer treated at M.D. Anderson or Sloan-Kettering. You are more likely to be diagnosed correctly and given the appropriate treatment at one of these cancer centers than at a public hospital. Medical treatment is already rationed, not based on availability of facilities or experts or drugs, but on ability to pay. Some consider this proper. They explain it in the same way they would explain why a poor man with a job paying an hourly wage drives a 10-year-old used car while a more affluent person buys a new Lexus. However, there is a real difference between a luxury car and the best medical treatment. If you cannot afford the car, you drive something with less flash and prestige. If you cannot afford medical attention, you die.
Perhaps in a country with very limited resources and a predominantly poor population medical care needs to be rationed and the few who are wealthy will have a chance to survive. But this is the richest country in the world. Many insurance plans that also pay for prescription medicines will only pay for generic versions of drugs. Generics are usually just as effective and safe as the brand name. The key word here is usually. Sometimes a doctor will see a need to prescribe a brand name without allowing for substituting a generic. If your insurance company will not pay for the branded drug you are out of luck. This is rationing of medical treatment.