You would think that as pragmatic as politicians are that they wouldn't want to mess with people's retirement. I don't have a 401k but do have a 403b at my current workplace, so I have no doubt that the contribution limit change would impact the 403b as well. Cutting the contribution limit all the way down to $2,400 would absolutely gut my ability to prepare for retirement (as least as I know it now), as my retirement formula would shift to:
$2,400 per year on 403b
$5,500 per year in Roth
$x,xxx in Vanguard brokerage account
2018 was/is going to be my first year maxing out my 403b contributions ($18,000 is what I intend to contribute). I don't consider myself to be "rich", though plenty of articles on this subject try to suggest that only the wealthy contribute at or near the maximum amount; I make $89k per year, live in a 1,300 square foot house and am trying to live below my means so that I can save for retirement, retire earlier (hopefully much earlier) than the "average" American and live the final 30+ years of my life on my own terms rather than the terms of an employer.
It would almost certainly totally change my future retirement date. I doubt that this will get passed but just the fact that it is being discussed as a possibility is pretty scary. I personally won't vote for any Congressional or Presidential candidate that supports a change like this that guts our retirement options. I just can't imagine why they would be willing to risk such a major backlash from voters.