The President of the ICC, David Morgan, has said that he will be surprised if the test matches did not become day-nighters in the next two years. He also added that it would be disappointing as well to not have day-night test matches, which seems the way forward now. 
The ICC had been planning day night test matches for some time now, but the biggest issue for the same ahs been the use of balls. Currently, the test match cricket uses red balls, but the same cannot be used under lights. On the other hand, it is difficult to use the currently used white balls – for the ODIs – because they get disfigured and discoloured much faster than the red ones, making the ICC mandate a ball change after every 34 overs of the game
Such a thing will not work in test matches. Hence, the ICC has been experimenting with pink balls in some of the domestic games. In fact, it has been said that even West Indies first class cricket will see pink balls being used for day-nighters.
Morgan also said that day nighters will be more vital in countries which are hot and have bigger stadiums – like Australia – than the ones which have cooler climate and smaller capacities like England.