Could Bitcoin Cash replace Bitcoin Segwit ?
It is a real possibility.
If you look at https://cash.coin.dance/blocks
You can see we are nearing quite fast to equality !
And if that happens, miners will switch, of course, they are only interested in profit.
What will happen then ? As Bitcoin Segwit doesn't have a difficulty adjustment algorithm for emergency situation, the chain might get really stuck for a while ....
Here a few interesting article on the subject:
https://medium.com/@malimujo/bitcoin-cash-bombshell-incoming-soon-44eee7d1fca6
https://steemit.com/bitcoin/@belerophon/the-black-swan-that-could-turn-bitcoin-upside-down
Anyway place your bet !