As we all know that bitcoin now are being made as a trading pairs to different fiat money all over the world. And we you go round the world having a good vacation on different countries you do not need to bring more fiat or physical money instead bringing gadgets and connecting to internet is enough to get fiat money after it will be traded to local exchange. In this way there is no need for one to bring more physical money as bitcoin could unify all fiat money around the world as trading pairs.
Unfortunately it can't be. I mean nothing can be but bitcoin definitely can't for sure. First of all lets take a look at why nothing can be global unified money ; because some countries are doing well and some are doing bad and even in euro zone German people hate Greek people because they lose the value of their money and Greek people hate Germans because they feel the economy is not proper because of outside stuff and Germans expect them to fix it.
Now, that we know even euro-zone is troublesome, global unified currency can't be done as you can see. Bitcoin is getting popular barely and when dollars and euros have been here forever and still failing, doubt bitcoin can do that.