I believe the difficulty would increase by at least 20% moving forward, too many manufacturer .
no not enough cheap power plants in the world for constant 20% growth.
barring a new magic .05 watt chip.
20 % for 24 months that can't happen . do the math
oh current predications
https://bitcoinwisdom.com/bitcoin/difficultyBitcoin Difficulty: 23,844,670,039
Estimated Next Difficulty: 27,061,375,299 (+13.49%)
Adjust time: After 785 Blocks, About 5.0 days
http://bitcoincharts.com/Difficulty 23844670039
Estimated 25580501467 in 785 blks
7.2%
So as of right now 7.2% to 13.49 %
These numbers are more in line with my thoughts on diff.
For asic builders keeping network growth between 5% - 10% is in their best interests.