The legalisation of Bitcoin is quite a complex topic. Exchanges can be regulated by various governments, and as they are similar to banks, this may be a good thing. The recognition of Bitcoin as a currency, or the restriction on its use are more difficult decisions for a government, and probably are connected to the security of the bankers who control the country. It is difficult to see how it can be banned completely. Will it ever become legal tender anywhere? Almost certainly not, as not everyone will have the ability to accept the transfer. Of course, if somebody invents a physical token that can be exchanged, then it may have the potential to become legal tender.