As I understand it the current plan is that the first of the new carriers is due to enter service in 2016 with only a helicopter capability. This is because, despite being new, it isn't suitable for the aircraft the UK wants to buy for the role. It was cheaper to build the ship than cancel it. The second ship will enter service in 2020 at which point the first will be mothballed and/or sold unless there's a change of mind within HMG.
http://seawavesmagazine.blogspot.co....ay-not-be.html
The whole thing is a shambles made worse by the harsh economic realities HMG inherited. God only knows how it'll turn out.