If I had known they would no longer duel at the time WWoHP was being designed, I would have said get rid of them then. For me, it could have resulted in a very different layout for the WWoHP, which, in turn, could have avoided the annoying intrusion on JP, and so on, and so on and so on...
As for now, without the dueling, I agree they are no longer unique. BGT has Montu, which is a better inverted than either dragon IMHO. This would free up a huge amount of space for a new coaster experience, something with a height requirement of either 44 or 48 inches. Of course, as someone said on this board, it's unlikely they will tear down a 20 million dollar investment anytime in the near future.