1) HD Cameras are too fragile for the harsh environments where they film the show, and it's too expensive bringing postproduction equipment to the remote locations; and
2) Have you seen how gross those people look after a month of no showers? Why would you want to see that in HD?
This season *might* be in HD. The reason I say that I watched the "CBS Fall Preview" show a few week ago. In that show, every Survivor shot was in widescreen. And when they did the interviews, it was clearly an HD picture.
That being said, just because it *might* have been filmed in HD, doesnt mean that it will get edited and broadcast in HD.
Actually they were testing filming survivor in HD this season to see what results they got. Whether or not that makes it to the air or not only time will tell.