Their digital tokens will be represented in USD and Euros primarily. For the time being these provide relatively stable forms of currency with low volatility(although the euro was more volatile than bitcoin week to week for the first 2.5 months 15' when it radically dropped in value) but just make sure you spend those currencies quickly as they aren't stable long term stores of value.

I'm absolutely positive Fiat will remain dominant for certain tasks like paying taxes and bitcoin has very little chance of ever replacing that role so these currencies are not at risk of being discontinued.... although some would argue the USD has failed and been replaced 2-3 times already so it is likely to continue failing like most forms of fiat historically.