The first thing that is sure is that mining is going to become less profitable - by 50%. So that mining rig set up that is earning 0.01 BTC per day is suddenly going to be earning 0.005 BTC per day - which is going to mean the costs of running the equipment in local currency might not be covered. This in turn should have two effects. The first is that a number of machines will be switched off which will mean that the hashing power of the network will come down and therefore increase the returns of the remaining profitable machines. There will be a shakeout of legacy mining equipment.