If bitcoin will hit $6000 then it will probably end up with $5800 or $5900 ethereum can hit $400 but that does not matter there will be bounce for me.
Normally cryptocurrencies price should not be correlated to each other but most of the time, it just follows the bitcoin price, and I agree with you if BTC will drop under $6000, ethereum price will drop under $400 unfortunately.
I never really understood the reason for this correlation, but it's very evident that it exists, so I agree with you. If bitcoin continues to go down, ethereum will definitely touch $400 or go even lower. On the good side though, once bitcoin starts going up again, which I believe it will eventually, the majority of altcoins, and that includes ether of course, will probably go up even further than BTC.