That really depends on many factors: who you are as a person, where or what you want to do, do you have others depending on you in retirement, do you trust in cash/banks/ or assets, and how long are you forecasting?
I would emphasize one fact to the people who scoff that the government would never sieze IRAs and 401Ks - Forbes documents that over 80 percent of the benefits to the top 20 percent of earners (the Tax Policy Center confirms this number).
Further, the Tibble vs. Edison case basically opened the door wide open for the Feds to say they have the justification for seizure, especially if we have a economic collapse.
That means that politically, especially in a crisis (economic collapse, massive natural disaster, martial law, etc) - people with retirement accounts are most likely going to get screwed, and the vast majority of Illegal squatters and American Takers will cheer.
The US Treasury has already "borrowed" $200 Billion twice from Thrift Savings Plan (TSPs) of government employees (during the debt ceiling and government shutdown), and said they "paid it back" - but it is all smoke and mirrors. The debt has been "frozen" for 150 days, and everyone knows it is a lie.
150 Days: Treasury Says Debt Has Been Frozen at $18,112,975,000,000
I can't tell you what to do with you money, only you can make that decision.
Yes, you could withdrawl, take the penalties, and put it into currency, but that depends on how much stock you put in paper currency. Every central bank, most economists, and now countries want to eliminate cash. The cash you hold could become worthless very quickly, depending on what happens.
Precious metals are a hedge, but even they are not a guarantee. First, gold could be made illegal to possess, transfer, buy, or sell - just as FDR did by Executive Order, Obama could easily do again.
But, they are a hedge against poverty.
How long are you forecasting? 10 years? 20? 30 years? Personally, I don't think we have that long. I am Christian, and I firmly believe we are rapidly approaching the End Times. Starring at charts and graphs that tell me "where I will be in 15-20 years" are akin to reading fiction novels, because I don't believe we will ever get there.
I believe the Rapture, and Tribulation, are coming soon, within the next few years, perhaps sooner. Judgments may come before the start of the Tribulation that even Christians will endure.
Therefore, my advice as far as money (and anything else) would be first to be prepared spiritually to meet Jesus Christ.
"Be always on the watch, and pray that you may be able to escape all that is about to happen, and that you may be able to stand before the Son of Man."
Luke 21:26
If you don't know Jesus as your Savior, you need to repent, give your heart to him, and be baptized. Pray that you are a sinner, and you wish for Jesus to come be the Lord of your life and to forgive you for all of your sins. You will receive the gift of forgiveness and the gift of the Holy Spirit - and eternal life.
Having secured that most important factor, I would next prepare yourself and your family physically, at least in the short term. If judgments come to America (and I think they are), then you should have some food, water, medical supplies, and home defense capabilities on hand. Store up treasures in heaven first, and then, store up your barns as Joseph did in Genesis 41.
Lastly, my advice would be to pray. Ask God what course of action He wants you to take, and then follow it.
Remember, if you are saved and one of His children, He promises to take care of His children. He never punishes the righteous along with the wicked, and there are many examples of this in the Bible (Lott, Noah, Egyptians, etc). We may see the judgment, but we won't experience the Wrath. That is reserved for the wicked and unrepentant.