Give your views will Bitcoin currency replace all the digital currencies and become the most used currency in future
Why you have to think about future to come to that conclusion ? Its already there.Maybe something like bitcoin would be used officially to buy stuff on airports and government organisations.Maybe buy train tickets with bitcoins.Pay for your bus fares with bitcoins.Hope you do get the point.
If he is asking for that then I think yes it will happen and will happen very sooner, the governments will accept it and will be allowed at the banks for financial affairs of the government, so then every coin will be replaced and there will be the royalty of only bitcoin.