Update (7 June 2016)
According to the website of the Council of the European Union, Bulgaria has now deposited its instrument of ratification (on 3 June 2016) to become the tenth country to complete its ratification formalities. Bulgaria joins Finland, Portugal, Luxembourg, Malta, Denmark, Belgium, Sweden, France and Austria as one of the ten countries who have completed their ratification processes.
The unitary patent system requires 13 countries to ratify including the UK, France and Germany meaning that just the UK, Germany and one other country are required to ratify to bring the unitary patent system into effect. The target date for the unitary patent system is currently May 2017.