BTC is now the base.
Most of the exchanges have BTC as prime currency to trade with.
If BTC will have the hard fork, means BTC will sink.
Is that means that all exchanges will now put ETH as prime coin to trade with?
I don't think so, The hardfork will be running in less than 12 hours for the BIP148, I mean the BIP148 will be deployed. But the ethereum will be a good place to save your money as far as i know to avoid the more dump in bitcoin.
I think the possibility is there.