Copter Weathervane Yaw Behavior

I have seen that there have been some recent developments in order to implement the weathervane mode also in the ArduCopter firmware. I saw the changes in autoyaw.cpp have been merged into Ardupilot:master.

Will this mode be available only in 4.4.0 or maybe also in previous new releases?

4.4 only, bit too big of a change for a back port to stable.