This is just a personal opinion of the person who wrote this article. I don't really think Bitcoin can be considered as being part of top currencies in the world. Base on my personal observation, less than 1% of the entire world population know the existence of  Bitcoin  and out of these percentage, only a few considers it has a currency for exchange of goods and services. The 99% left do not have a single idea of what Bitcoin is and even think about using it for their transactions.