How is this News or Rumours?
Of course GK will replace DH. How can you use a 3rd edtion GK when there is a 5th edtion GK now? How about Brother Stern? Same names, different edtions. All that is changed is the Title, but the names in the Grey Knight Codex replaces the names in the Deamon Hunter Codex. Title change doesn't cut it for me, sorry, you will have to use 5th edtion if playing in tournies. Of course if you play me in a friendly game, you can use what ever you want.
But come on. Title name change? I just find it funny how all the names inside the book are the same, with new ones added.