Well if you look at the bitcoin hash rate using a block explorer like the one im linking below, you can see varying indicators and averages showing that bitcoin's hash rate isn't decreasing over time and in particular since August's 1st BCH Hardfork, you see the hash rate increasing. Why? Go Figure (aka I don't know cause network effect maybe? i.e. poeople in countries like russia and korea joining the network at a greater rate? idk)
RE: Miners are quietly moving to Bitcoin Cash(Huge threat to Bitcoin!)