John,
I look at it differently. I think the PGA Championship is differentiating itself from the other majors by hosting the event at modern courses, such as Whistling Straits, Kiawah, and perhaps Colorado GC in the near future.
This is more interesting -- at least to a spectator interested in golf architecture -- than seeing the PGA played at places like Oakland Hills, Oak Hill, Winged Foot, et al only a few years following a US Open played at the same club.