Bitcoin mining difficulty adjusts every 2 weeks. This allows the block generation rate to remain at a constant, around 10 minutes.
For only the 7th time in the past 2 1/2 years, the difficulty is going to drop. This will happen in the next 24 hours.
Bitcoinwisdom predicts a 4.68% drop: https://bitcoinwisdom.com/bitcoin/difficulty
If you are currently mining, either with hardware or cloud mining, you should see a 4% increase in your payouts the next day, and for the next 2 weeks. This assumes that the price of Bitcoin remains the same.
The reason for the drop is that miners are abandoning Bitcoin, and starting to mine Bitcoin Cash. You can see here, the hashpower of Bitcoin Cash is growing exponentially:
https://bitinfocharts.com/comparison/bitcoin%20cash-hashrate.html
And, the hashpower of Bitcoin has dropped equally:
https://blockchain.info/charts/hash-rate
Does this mean that miners are abandoning Bitcoin all together?
Probably not, it's just that Bitcoin Cash difficulty dropped so low last week, that many miners moved from mining Bitcoin to Bitcoin cash. The miners are in it for the money.
With the increase in hash power moving to Bitcoin cash, I think you'll see the difficulty jump for mining Bitcoin Cash over the next 2-4 weeks, and the miners will be moving back to Bitcoin shortly.