Yes quantitative easing is a real issue in fiat based economies. Nevertheless, there is a lot more to a currency than supply and demand side economics. For the most part, a currencies value is determined by a mix of GDP, other countries holdings of the currency in question and national debt.
In countries like the United States GDP usually is the strongest determinant of the countries dollar value. The more they can keep trade surpluses in the black, the greater value their currency will poses. However in turn, the stronger their dollar is in contrast to their trading partners, the less enticing their export become. I agree that crypto currency is a great alternative, but I still think that it has a long way to go before it takes over other more established currencies like the pound or the US dollar.
No need to wait for it to 'take over'. As long as it holds value better than the dollar and insulates me from the forthcoming bubble I'll be satisfied.