It seems like many of the classic NGS photographers have faded into the landscape. I'm not convinced it's a question of switching equipment, but perhaps there is something to the fact that photography budgets are shrinking drastically, and many photographic subjects have been covered extensively already.
Steve McCurry does a lot of commercial stuff now, which pays MUCH better than an NGS salary. Follow the money.
I like McCurry very much and DAH, but it seems the current trend at the geographic for photography has followed other photojournalism...lots of distorted close-in wide angle stuff. A lot of the more artful photography has faded and been reduced to ultra-wide-zoom PJ-style.
Quickly watch the slide show that plays here http://www.nationalgeographicassignment.com/
...I would hazard a guess that most of those shots were made with a 35mm or 28mm lens. These days, everything is made with the 14-24 or 17-35.
It would be nice to see NGM return to it's heyday of the 80's and commission photographers with a more graceful, art-filled eye. I think bucking the ultra-wide PJ trend would, once again, set their photography apart and make it more memorable. Certainly, my own opinion