Bitcoin has never been the most profitable to mine. It's always been a flaw. For that reason, I think that this logic is flawed. In reality, we will see miners leave, but are we going to see troves and troves of them leaping to BCH? Doubtful, because all of the value-driven miners would be mining Zcash and ETH and the numerous other coins that are much more profitable already. Of course, this is looking strictly from an electricity to value ratio, not taking into account the speculation of appreciation. This is likely why Bitcoin still has many many miners because people believe in its appreciation since it is the forefather of blockchains.