have you met the retirement age? if "no" then dont. if you are scared of a market decline, dont be...if there a crash, it will return after a few years.
Discussion
It might return, bitcoin is going up for ever.
dont be too optimistic there buddy. if there is a major recession...ppl will dump their bitcoin for hard-cold cash. i dont know of many places that accept bitcoin over cash to pay the rent or the mortgage. we'll see how bitcoin fares during a major recession and with unemployment over +10%.
Pleb not, idiot: yes.
Also if you have your 401k in bitcoin you can cash some of it out for cash.
You can not do that with your 401k as easy as you can bitcoin.
Oh holy central bank, please backstoppeth thy stock market! Amen.
I am specifically dumping my 401(k) for cash to inject capital into my company.
If I was in a place to sell my business, I would, I am in a place where I need to grow my business; my 401(k) is the easiest access to capital with the lowest tax burden 
I’m not concerned about a market crash, im not much concerned about anything, I have bitcoin.