If you are very interested in investing in Bitcoin in your IRA you can easily do it and no one is talking about it. IRA stands for Individual Retirement Account and you can put $6000 a year into it as a US worker. If you have a Visa and are allowed to work here, have a Green Card, or you are a US citizen you are able to open an IRA in the US.
Now investing in BTC right now is expensive. You can invest into GBTC which is Grayscale's Bitcoin Trust ticker symbol. Right GBTC sells for $12.70 a share and is backed by Bitcoin reserves that Grayscale holds.
You can currently invest in GBTC on TD Ameritrade's IRA Platform. Other platforms are probably viable for this, but I only know that it works on TD Ameritrade.
Now investing into BTC in your IRA is amazing. Once you turn 59 and half you can take money out of your IRA and it will be not taxed a cent. If BTC heads up to $10,000,000 and you have it invested in your IRA then you won't be taxed a penny on it once you hit the age 59 and a half.
The downside as mentioned before is that you need to pay a whopping 37% premium to invest in BTC on TD Ameritrade for your purchase of GBTC, but if you are a bull and want to hedge on BTC exploding and having retirement savings that are plentiful in the future and that aren't taxed GBTC is a decent option to invest in now until you can invest in actual BTC sometime in the future in IRAs, but that will likely take a few years before the American public will be able to do that, so in the meantime GBTC is the best option we have.