Can someone tell me how long it would take for the next new block if hash rate suddenly dropped by 50%
If the difficulty drops by 50%, then blocks will be produced twice as fast, assuming that total hash doesn't change. However, because the cost of mining a bitcoin has halved, miners may switch from BCH, increasing the total hash power, and blocks will be even faster.
Thanks for that. So now I know that the block rate is a linear correlation to the difficulty.