The "promise," such as it was, was that no one currently receiving SS benefits would have his benefits reduced. That promise stands today. Those benefits will never be reduced.
HOWEVER, in order to sustain the "Trust Fund" for everyone will retire in the future, some changes are needed. First, of course is the increase in income subject to the payroll tax - maybe even eliminating the cap altogether - but it is also necessary to incrementally increase the retirement age. This has been going on for a long time, and lifespans continue to increase.
I could not get "full" retirement at age 65 as my father did, and my son will probably have to work until 70 to collect full benefits. But his generation will live many years longer than mine. Do the math.
An increase in the retirement age is not a cut in benefits. More importantly, SS is unlike other Federal entitlements in that Congress is PROHIBITED from spending General Revenue funds on SS benefits, so the fund MUST remain solvent, or it will revert to a pay-go system, which WILL reduce benefits by 20-25%. This stuff ain't complicated.