Currently, anyone receiving a paycheck  has 6.2% taken from it to pay into Social Security until their income reaches $137,700. Once it reaches this amount the deduction for Social Security tax stops so the wealthy get an automatic 6.2% raise. The wealthiest Americans, those who earn  $137,700 or more do not pay into the system, yet they are eligible to collect from it. 
This income cap should be removed so that the wealthy also pay into the system. The revenue gained from a 6.2% tax on millionaires could do much to keep the system running well into the future. There are so many retirees who have only their Social Security incomes to live on. 
An even greater benefit would be not to take any Social Security tax from the paycheck of anyone earning less than at least a poverty level income. This would provide more funds for our lower income families to live on in these difficult times.
If there should be a cap of any kind, it should be that anyone earning above a certain amount, say maybe $250,000, does not collect Social Security income. 
These changes require support of the congress and senate, politicians who are dependent on funding by the very wealthy. It won’t be easy, but perhaps enough pressure from constituents will have an impact.