No way ETH will fall to 400$. If you watch news of last month with ETH, there are no bad news. Buterin is not sitting straight on his ass. His team making and working a lot. He's donating his own funds to protect against robots revolution.
Take a look of ETH PoS Casper. When PoS will come live, it will be the end of PoW mining ETH with GPU, so the only thing to generate ETH will be PoS and it will rise the price up. Also This will entail the influx of new investors.
So the price falling is no more than just a rumors. ETH will rise with BTC.
https://www.reddit.com/r/EtherMining/comments/6t56a0/important_information_from_todays_ethereum_dev/