By this time that thing may not happen.But in the near future,yes bitcoin maybe replaced by other cryptocurrency.Maybe by ethereum or litecoin or any other alternative coins out in the trading platform.
It is not impossible for Ethereum or other Cryptocurrency to overtake, but replacing seems quite impossible. Moreover, People are generally indulged in Bitcoin more than any other one. And new people usually gets to know about Bitcoin when they know about cryptocurrency and the use of it is also quite wide in the market. So I think it is very tough to replace Bitcoin or overtake.
Nothing can replace Bitcoin (altcoinwise). Mainly because of the fact that Bitcoin suits the needs of the majority of the people. People don't need gimmick features that altcoins are offering. People just want the simplicity of Bitcoin. So far, there have been plenty of so called (according to people) "Bitcoin killer" altcoins, but they all haven't done anything significant other than functioning as a speculative investment tool. No one with a well functioning brain think that altcoins have the ability to replace Bitcoin.
I'm inclined to disagree
As I already said before, to make a Bitcoin killer coin, you would have to hit where Bitcoin is the weakest, since the chain is not stronger that its weakest link. Right now, it is not some feature or a set of features that are lacking in Bitcoin, but the development process itself which is pathetic at best. All that infighting between developers has already led Bitcoin to stagnation. In this way, of you want your coin to succeed and potentially overtake Bitcoin, you should start by working out the best (optimal) way of developing it, i.e. how it will be updated, what kind of consensus should be needed and things like these. Since you can't even imagine what features will be in demand in the future, your coin should be flexible but without wreaking havoc after an update is applied
