If BTC prices continue to decline, it will automatically all coin prices will also follow BTC, will decrease as well, including ETH. If in such situations, as much as possible I will choose both. BTC and ETH are the best coins to invest, so with the opportunities that exist when the price drops all that I must be able to use well to be able to have both. However, I think it will be difficult for ETH to surpass BTC, because over the development of ETH then at that time BTC also has developed rapidly.