They won't have to adapt because that won't happen. Governments won't allow such situation to happen because they are actually holding the control and not the common people which are holding the decentralized currency. As much as I would like for the Bitcoin to be implemented as a currency within all countries I  know that this situation won't come to the light.
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There are too many people which don't even know how to manage the physical money; how would they in this matter manage the digital?