How do you even know what the "hacks" are planning to do? (My guess is to make Mike a woman, but we shall see). Yours is a knee-jerk response that no one should take seriously. We disagree about the current Oklahoma!, but that's not the point.
Theatre is a living and breathing art, not a museum for static artifacts, trapped in amber (and it's not like The Philadelphia Story IS a timeless classic anyway). And presumably they are doing whatever they are doing with the approval of the owners of the rights. If it's in public domain (doubtful, given when it was first produced--the latest works to go into public domain recently are from the 20s), all's fair.