The cardinal rule in investing is:
DON’T PANIC.
(Coincidently, that’s also the first rule given to travellers in The Hitchhiker’s Guide to the Galaxy.)
Cashing in a 401k before retirement is probably a really, really bad idea. The odds of armageddon happening in the next few years are pretty low. However, the taxes (between 15-35%, probably at the higher end) and penalties (another 20%) on withdrawal are dead certain and permanent.
Almost every 401k plan allows the individual participant to select mutual funds from a list of funds. So, you think Ben B and Timmy G are going to wreck the US$? Then get out of the bond (AKA, fixed income) funds and re-allocate something like 50-50 to the international equity fund and the money market fund. If you have options for an international bond fund or an inflation-protection fund, include those also. It’s unlikely that a 401k would have a fund concentrating in mining, petroleum or natural resources, but that pick would also be an obvious candidate. If Ben B and Timmy G successfully ruin the US$, the international funds get currency protection and the US$ MMF eventually gets a higher short term interest rate. It’s highly unlikely that Ben B and Timmy G will do as much damage to your 401k’s value as you would by cashing it in.
DON’T PANIC! Just be sure to get out of any fund that has the words “intermediate bond”, “long term bond”, “fixed income”, or “20xx target” if you have concerns about the competence of the ruling elite.
Instead of armageddon, I'd use terms like financial collapse, a devalued worthless dollar or confiscation. But, you base that on what?