BTC can't be replaced, at least for now. He's like a flag, but different virtual currencies have different focuses. Like ETH smart contracts, Zec is strongly anonymous
Bitcoin wont be replaced by any other crypto currency,i do accept that and in fact ETH is not a currency but a smart contract platform,but when it comes to Zec ,i really doubt it is really an anonymous currency at all,i heard some fishy things about their vision on how to install a backdoor and so on,so i will strongly avoid the coin and try monero or dash.
yes that is right that bitcoin wont be replace by any other currency but will continue for a long time. i am sure that bitcoin is the best crypto currency of the world and will always remain as the number one currency of the world.