Here is a chart that you can use that will help.
I have updated it with Bitmains latest offering of the Antminer S9.
It seems that the network difficulty will be dropping. Perhaps due to BCH taking a little of the mining hardware out of the picture or older hardware being taken offline to to operating costs.
To clarify the chart I have is set to have an increase in difficulty at 1% every 18 days. THIS IS AN ESTIMATE. It may drop % a few times. However I have factored in the average increase over the last two years and even the average from the last year.
https://docs.google.com/spreadsheets/d/11QS1BBV11KNGTF8N_-fdfmjTZ3WzPQFbLfVrl5n6R8s/edit?usp=sharing
https://i.imgur.com/v4xu4s1.pngGreat work, goes to show some naysayers here talking about Avg 15% increases... Some ppl are very naive to think big mining operations will run at a loss based on faith of a bitcoin price increase. Fact is mining will always be profitable, the only way a S9 becomes unprofitable is if something REALLY good is released in the next few months and they flood the market with it.
That is very possible. Mining is not good now. Alot of things can happen before breakeven occurs. Currently, break even is longer and thus, risks are far higher.