When I was there last week, the paddock was looking rather bare, and very muddy. It's at an area of the zoo, that water slopes down into and I would imagine that the PSD have been moved, so the paddock can recover and be rested. I don't know this for fact, but when I was there last week, I couldn't help but think the paddock needed a rest.
Given the old Bongo paddock (or Warthog paddock) is effectively on the HOF footprint, I would expect this move to be temporary and that they will move back to their normal exhibit in the spring.
I don't know this as fact, so don't take as gospel, but I would be surprised if something moved into where the PSD were as the paddock does need rest, and of course they share the Indian Rhino House, with another Deer as well, so if something else was put into that area, it would need to be compatible on that front to.