If the dollar falls I think there will be only one thing can happen with BTC is Bitcoin price will go to the moon 
). But I think this case will never happening cause dollar will never being replaced by Yuan
). But I think this case will never happening cause dollar will never being replaced by Yuan It is meant in global point of view. You can use dollars in Eastern Europe, Africa, South America, Mexico. And I am sure that people will start using other FIAT. Yes, BTC will fly to the moon, but there will be still people who will use classicall money.