Bitcoin's definitely gaining traction as an investment option, especially for the long haul like retirement planning. It's got potential for growth, but it's also pretty volatile, so it's smart to approach with caution.
It's always to approach anything with caution, but remember that we are talking here about Bitcoin as a retirement bet. It's not about getting-rich-quickly scheme, rather it's about what are you going to get from your investment in Bitcoin in the long run. We can look at history of Bitcoin and see that so far it was a good decision to invest in BTC. Very good, I would say. And considering that most people in the world are still don't engage with Bitcoin much, we can conclude that in the future, when they realize that BTC is a valuable thing, it's price will rise.