If BTC will have the hard fork, means BTC will sink.
there i no if and there is no hard fork.
there is only a soft fork for bitcoin on August which will activate SegWit because it currently has a very high support from the miners (nearly 90% support and it only needs 80% so it is already over the mark). and when it activates like this there won't be another chain. there WILL BE ONE chain only and price will rise up faster than you can blink.
Is that means that all exchanges will now put ETH as prime coin to trade with?
even if bitcoin dies right now, nobody will switch to a shitcoin like ETH. nobody even trust ETH anymore. everyone knows how unreliable its network is. how their transactions are going to be stuck and their money to disappear easily because it is buggy. exchanges have already disabled ETH wallets. and as you can see ETH price is dropping hard.
the second best thing (like always) is litecoin and always will be litecoin. and if someday we decide to replace bitcoin we will do it with LTC but that day will never come as i said by August 1 we will have a smooth 100% soft fork without a chain split.
Calling Ethereum a shitcoin is just making no sense..
It is faster the bitcoin and almost every new coin/token is based on Ethereum for a reason...