Carnival first came out back in January and said "On all ships by Spring 2013". Then when that came and went they said by Summer 2013, now the latest was end of Summer 2013. The only thing that hasn't changed is they continue to say it will be fleetwide, but it seems the timeframe is still up the air.
It's currently on 21 of the 24 ships in the fleet. Which currently leaves the Carnival Pride, Carnival Splendor and Carnival Spirit without Faster To The Fun.
Even on the 21 ships where it has been offered, there are still some departure ports and some itineraries where those ships will not offer FTTF. San Juan, as of the last I heard, was still one of those ports that does not offer FTTF, but I do not know why.