Well, US Dollar still popular and still the best currency such poundsterling and euro, i think this 3 main money will keep the best. For bitcoin, it can be our new world currency though. but we need to motivate other people to use bitcoin.
Yeah, there is no doubt that US Dollar is till the world currency for at least 30 years later. Bitcoin need to do many things to prove that it can be able to replace USD in the future. Now, bitcoin supporters have to work with 100% efforts in order to increase Bitcoin reputation and introduce it to many other people.