Social Security is not going to be unavailable. The benefits need to be altered do to serious actuarial problems. Possibly altering the age in which you collect. Or returning it to the way it was originally designed as an individual account. But it will not dissapear altogether. It is highly probable the age to collect will be adjusted up for full benefits, which currently start at 66 for younger workers. When the plan was designed the average life expectancy was only a couple of years beyond the full benefit date. The plan was never to pay people 25-30 years of benefits. That is a recipe for disaster with a retirement fund that has no capital investments. It is mathamatically impossible to keep up with inflation. Even with the proper investments, well run pensions are having similiar actuarial problems with life expectancies increasing.
The most important thing for future retirees to do is focus on other forms of retirement planning and try and save at least 10% of their gross income per annum. Preferably in tax sheltered sources. SS was never designed to retire on as a primary income source. It was to supplement your retirement. It is the citizens responsibility to cover the majority of their retirement planning needs. The sooner you start the more powerful the effects of compounding tax deferred growth will be.