The other scary possibility is that we could see runaway inflation in the future.
This could happen if future presidents and future Congresses are determined to pay all promised Social Security benefits come hell or high water. In that case, they would simply run the printing presses overtime to create the money to pay the Social Security benefits as promised. The fact that they will be devalued dollars will not matter. The only thing that would matter would be that the politicians could claim that all promises made to Soc. Security recipients have been kept.
Another factor will be that all future Presidents and Congresses will look at the problem in two or four year increments, corresponding to election cycles. And they will look for ways to take care of paying benefits for the next two to four years, without considering a long term solution.
Social Security and Medicare/Medicaid are government programs that give the Federal government a lot of control over the finances of elderly people in this country -- along with the tools necessary to dictate when they die.
A person who collects Social Security and has a lot of medical expenses has given their fellow citizenry a huge financial incentive to let him die force him to die.