I think more and more that Bitcoin is acting as a kind of reference point and is not meant to take over all currency transactions; fiat is already capable of doing that within country borders to a considerable extent. Certain cryptocurrencies will prevail as the chosen ones to extend this there where fiat runs into roadblocks (checks, fees, delays, etc). Or fiat may fall out of grace if central bank actions erode confidence in fiat currency further. 'No fees' currencies like IOTA and RAIBlocks are already banging on the door.
All that Bitcoin has to do, is continue to function beautifully.