The IMF already uses some form of supranational currency to make up for the limitations of sovereign currencies.  Keynes proposed a supranational currency called Bancor, and while it was never implemented, SDRs are a close analog and currently in use by the IMF.  It's therefore extremely unlikely that we would see radical change like Bitcoin becoming the standard supranational currency when we have in practice something that already mimics the effects of doing so, and radical change like the kind you talk about will lose out to the inertia of "good enough" every time.