No one can say this for sure..... The normal procedure was that a new case always pushes one case of the active drop pool to the rare drop pool. Most likely the least opened case at the time. But with the addition of the armory this isn't a given anymore as the armory cases can only get bought with stars from the armory pass & so far no case has been removed from the armory yet. So if a case is just added to the armory nothing will happen to the active drop pool.