It's already official, they will release DayZ on it.
EDIT: I actually think, the producer of DayZ just test it on Arma II. How big their Community would be, how do the player react to this kind of realistic simulation and then, when the gameplay is perfect, they just have to overwrite the new graphics, the other stuff (animations etc.), and the new map of ARMA 3.. then they're done
The advantage of the engine is that it's easy to port the mod to a newer game. FDFMod as an example, It's been released for OFP, Arma, Arma 2.
So yeah, I think he is just testing it on Arma 2
Thats what i thought