Countries may abolish an anchor currency because the import of the anchor currency’s monetary policy is leading to rising domestic macroeconomic imbalances. In the history of the global monetary system, this has been quite a usual event (Frankel 1999). It merely indicates that one monetary policy does not fit the size of all countries pegging to the anchor currency.
By contrast, a decline in demand motivated by rising distrust in the stability of the respective anchor currency per se, in particular, its domestic stability, is a very different scenario. Such a scenario could have profound implications for the international role of the respective anchor currency. However, I do not expect this scenario to materialise.