For what its worth, I called the Wharton Adcom out of sheer frustration once I got notification of my Summer WL. status. My question was on the fate of International Applicants given the July 18 final notification date.
They called back a few minutes later and said they would certainly be considering the peculiar circumstances of International Summer Waitlisters in making their admit or ding decisions. So I don't expect any international student will have to wait till July 18 before getting some sort of closure.
I assume there will be at least some priority given to international waitlisters in the admit/ding decisions.