For bitcoin, you still need to improve the speed of operations and make it possible to use it anywhere in the world. While it will be only an additional currency.
Yes I agree on this. Bitcoin will not be as a currency of the future rather an additional currency only. Fiat can't be replace of any crypto currency, whatever will happen nor whatever it takes.
However, bitcoin will always be the future as long as many people patronize it, merchants still using it and I don't see any reason that btc will die in the future.