That will be a very bad move in my opinion. Because ETH is already quite overpriced (I am not talking about its exchange rate versus fiat, but about its exchange rate versus BTC). And also, alts such as NEO and ADA are giving ETH quite a lot of competition.
Actually bitcoin is the king of all coins, if you want to exchange your bitcoin to buy some ethereum that would be a bad move for you because once bitcoin is down the other coin will also be down. Eventhough ethereum is the second coin next to bitcoin, you should always stay at the king right?