I believe that the answer is yes, as a 'black swan' investment.

As I see it, in 5 years there's a 20% chance that bitcoin will be extremely valuable (more than 10 times its current value), and 80% chance that it will be worth between 0 and its current value. If you agree with this observation, and you have an appetite for contrarian investments with a huge upside, then it makes a good investment in relatively small quantities (1-2% of your capital).

Consider the following:

• 3 years ago bitcoin was an esoteric invention that only few hackers have heard about.
• 2 years ago people started to discuss its implications, legal position and the entrepreneurial opportunities around it.
• Today (early 2016) the financial media reports about it alongside other currencies and commodities in days of market volatility. Regulators are taking steps, some theoretical and some practical, to define it and deal with it. Those who haven't banned it assume that it's here to stay. Hundreds of well funded companies in the world are tackling problems in this emerging ecosystem. The bitcoin transaction rate goes up and its volatility has been relatively tame during 2015

I believe that this brief history makes it obvious that bitcoin might reach the financial mainstream in the long term. Not in a sexy, big bang way. In very slow and consistent baby steps. Time is a wonderful way to stress test ideas and innovations. Bitcoin has been around for some good years now. Chances are getting better that it's here to stay as the 'king of cryptocurrencies'.

Maybe it will never get to the mainstream. Maybe it will and then the road will be long and bumpy. But for the 20% chance that it will happen eventually, I think it makes sense to buy it and hold.