I was thinking, they are pretty close in appearance, that the announcement of releasing Mk.VI may steal sales away from Mk.IV.
Maybe release Mk.V first, let that prolong the hype generated from Mk.IV, then release the Mk.VI once there are no more Mk.IV's available at normal prices and certainly before the Avengers movie gets out. It's fun to guesstimate.
The mark V is still fresh from being announced..there is no way in hell the MV will be out before the VI!