I don't think it will replace bitcoin. there are better alternatives for Bitcoin than bitcoin cash.
And if the lightning solves the the issue like they say, it will become hard for Bitcoin Cash
No coins would be able to replace bitcoin. Few top coins would try minimising the long gap by gearing up. The tops coins are on its way to. But it's really hard to. ETH is on its next to bitcoin and above ETH as per coinmarketcap.com. ETH seems to be setting it's value high this year. Let's watch the coins grow.