i dont know if it will "kill all currency" as you stated
it will be an alternative option
it might kill paypal and western union though
No, it will kill all currency.
More and more people will continue to understand how currency and medians of exchange work in the first place.
As Bitcoin grows, this will inflate ALL currency on a GLOBAL scale because putting money into BTC is causing domino effects that is massive.
People won't take this for long, and something will be done about it. Either BTC stays or
traditional currency once in for all crashes. Remember, if the USD crashes, this will have huge global effects like you would not believe. What if the EURO crashes? Same thing.
They both cannot and will not sustain stable growth along side eachother.
One side has to crash once and for all, BTC is not the same as these other medians for exchange. It isn't that type of currency. Bitcoin isn't the same.
This goes for any "alternative" to BTC.
BTC can change and adapt to any other currency if the population agrees to it. Any other digital currency like Bitcoin is just being used as a ponzi that will without a doubt fail, but is also completely legal based on what actually defines a ponzi.