History teached us how many good projects are out there, Bitcoin will always be the first but it's only a matter of time and coins like Zcash will have mass adoption.
Most probably you are wrong. I'm very much sure there no altcoin will be capable to replace bitcoin by any means.
Like many people said here,
They are just applications whereas only bitcoin is the true currency.
We are in need of a currency system not just applications. Bitcoin is the best a currency for present time itself and it is going to be more perfect in future.