Medicare taxes are withheld on all earned income, but Social Security taxes are only withheld on earned income up to a ceiling. The 2010 ceiling was $106,800.
If the ceiling had been removed and Social Security taxes were withheld on all income, receipts would have increased by an average of 23.6% over the past 10 years.
If we remove the ceiling and project that magnitude of increase into the future, it would add about 1.1% of GDP to revenues. This would only delay the point at which Debt reaches 100% of GDP by 3 years - from 2023 to 2026. This assumes there is zero corresponding increase in benefits for those who pay the additional taxes.