The US dollar has been on a continues value decline because of US excessive growing debt profile and the unwillingness to pay off the debt in the sum of trillions of dollars. Some angry countries are started looking for a way to bypass the US dollar in the international market, which will further affect the US dollars. We don't know when the dollar will become totally useless. Let's hope there is a policy change and they stop mass printing of the dollar.
No matter how far it declines, it will always be perceived as the most important currency in the world unless the US government does something extremely messy(Low chances) which is why it is simply wishful thinking that BTC will replace it in the future.
The debt will go down over time and countries won't simply boycott the dollar considering the interconnections between it and other global currencies. If it were to collapse, the world might get plunged into a horrible situation.
