I believed also that sooner or later bitcoin would be legal in the type of transaction, as a matter of fact there are some big companies who already accepted bitcoins, and i can say that they are the leading model for the better future of bitcoin.
Actually, the use of Bitcoin in almost 70 countries is legal and to name a few these are Norway, Poland, Singapore, Slovenia, South Korea, Spain, Switzerland, Sweden, Turkey, United Kingdom, United States, Australia, Belgium, Brazil, Canada, Colombia, Croatia, Czech Republic, Cyprus, Denmark, France, Germany, Hong Kong, Israel, Italy, Japan, Ukraine, New Zealand etc. Being legal in those countries people used it in any type of transactions, e.g. trading, shopping, exchanges, etc. However, for Bitcoin to become the world's leading currency I have no idea.