In order to assist customers in a geograhpic area where we do not yet have a large number of proprietary ATM machines, we are contemplating waiving a portion of our foreign ATM fees, as well as rebating a portion of the ATM fees surcharges of the foreign ATM operator, until we have a greater ATM presence. We will be notifying affected customers of this new benefit, but will we also need to notify affected customers at some future point prior to reinstating the fees that were originally disclosed at account opening??

I would say yes, since you are "telling" them that you will be waiving them. If you didn't tell them at all or told them that you "may" waive the fees, then you wouldn't need to redisclose.