I doubt that bitcoin will ever become mainstream like any other government regulated fiat currency because bitcoin is not structurally build that way. It has already created a parallel economy around the world but the legal status is still not clear in majority of the countries. While Holland has legalized it and Japan has started showing interest in legalizing it, but that will be just another currency inclusion in to their economy. It is far from being mainstream.

Also the major threat for bitcoin is the banks and organized financial institutions. They are loosing business because of crypto currency. The money invested in cryptos are mostly not channelized through the banking system. So they will try to create pressure on government and speak for banning bitcoin. So the road is still long and we have not completed even a quarter of it. Till the time governments don't show interest on bitcoin, is good for us.