it would be a useful bit of statistics to do, to count the number of vendors you can find in the world, and gather their currencies, and then count them all and figure out what teh actual global ranking for "currency" actually is

USD is definitely the top dog, and euro is not far behind, but yuan, ruble, and, yes, bitcoin

bitcoin is probably actually in the top 20 of most accepted currency, by number of merchants

bitcoin is rapidly being adopted as an accepted means of payment in very large numbers in countries where the size fo transactions is a lot smaller than in the rich countries, mainly because there is so much more people outside the rich countries, and because those poor countries are more likely to be suffering from debased national "currency"