Considering that BCH is just a fork from the original Bitcoin blockchain, it may never replace it, the same way ETC never replaced the original Ethereum.
if you do believe that then why did you even start this topic!
also ETC is the original chain and ETH is the fork, LOL
and the main difference is that nobody wanted either of them. the community was already split because so many lost money because of the ETH bug and so many others didn't or even if they did they believe that a "roll back" which was the only reason for the fork is a terrible idea.
Therefore, I believe that in the future both of these cryptocurrencies will co-exist (Bitcoin and Bitcoin Cash) providing people with options whenever they want to quickly send a transaction or just secure their investments for the long term. Whenever it is Gold (BTC) or Cash (BCH), there will always be a choice for anyone to transact in this rapidly evolving technology. Just my thoughts

bitcoin cash transaction speed is the same as bitcoin! you forgot that it is the fork of bitcoin with nothing different regarding "transaction speed" which is block time. and if BCH is also spammed it will become the same slow one during the spams.
and i agree, it will exist the same way Pandacoin, Rabitcoin, Dogecoin, HTML5, GAYcoin,... are still existing alongside bitcoin.