My 401k is one of my big money concerns. Not so much that they will lower contribution limits, as I'll just put the money else where, but that they'll do something to raise taxes, or institute a fee on existing balances. It's actually my largest asset, by quite a bit, as for many years it was my only savings. I worry that they will tax 401k withdrawals at a higher rate going forward or do something to penalize those with higher balances (compared to the "average, less than 10k in savings" person), also there's a strong chance I will not live in the US during retirement, so that's another avenue of revenue - higher taxes for non-residents.
On the other hand I don't want to lose out by giving in to hysteria. This year I really pulled back on my contributions but then worried that was the wrong thing to do, so did a massive push to max out (which I missed by 2k).
What to do? There's a lot to consider.