If they were being honest, it would be something like 30th Ed, right?
Anyway, I suspect they'll want to keep numbers off it to make it conceptually easier for a new audience to buy into - by calling it 5th Edition, that's four editions people have potentially missed out on stuff of, whereas just calling it Next, or Kumquat, or Modern Warfare, implies that it's a fresher start and easier entry point.
I suspect they'll try their best to just brand it Dungeons and Dragons.