What they are considering is lowering the maximum allowed contribution. It's currently $16,500/year, with an additional $5,500 if you are over 50. You simply won't be able to contribute as much in the future.
The claim is that it primarily benefits the "rich". The problem is: that's peanuts to the "rich". What's really happening is that the upper middle class (like me) is socking away as much as possible in preparation for retirement, with the expectation that Social Security is going to be "means-tested" out of existence for me.
This could quickly become a middle class vice - means testing Social Security excludes those with any savings and likely property (like Medicaid today for nursing home coverage) while limiting contributions makes it hard for those except the top 5% to save much.
Little to no SS, little to no private savings, totally abandoned to the Alpo diet.