The Dune Universe: extended or not?

For the last few months I have been absorbed by writer Frank Herbert's ultimate creation, the universe he describes in his Dune novels. Completely the opposite of the future vision of Star Trek, "Dune" is a violent, cruel and sometimes vicious worldview, in which the long term survival of the human race is described against probably its worst enemy, humanity itself.
Now Herbert himself wrote six novels set in this universe, thereby spanning several thousand years of fictional history. These works are rather philosophical in nature as Herbert explores his political, social and cultural ideas. That, as well as his brilliant command of language makes them quite a difficult read: very much worth the effort, but one really has to make that effort.

At the time of his death, rumours had it there existed an ouline for a seventh, all-concluding novel. As the final novel, Chapterhouse: Dune, ended with a tantalizing "cliffhanger", most fans were despairing whether they would ever find out what Herbert's idea of the conclusion would be.

But since Chapterhouse, a lot has happened and is still happening. Very much in the same vein as what happened to J.R.R. Tolkien and his vast heritage of unpublished works, Frank's son Brian has taken over his father's legacy and is producing new Dune novels, together with co-author Kevin Anderson. First, a trilogy which formed a prelude to "Dune" itself, telling the life stories of its main characters from the three main families in that book, Atreides, Harkonnen and Corrino. Then a truly audacious effort with another trilogy which told the story of the Butlerian Jihad, the war against the thinking machines several thousand years before "Dune". And then came the long-awaited seventh and concluding book, published in two volumes : Hunters of Dune and Sandworms of Dune. And currently, more stories are pouring out, which are set in the various time periods between Frank Herberts original novels.

Now the father is not the son, and there is a very marked difference between both. The original "Dune" novels are mostly philosophical, meaning that there is comparatively little action and lots of talk and thoughts. They are written in a very economical language, not a word too much! With the new material, it is exactly the other way around: mostly action and little room for philosophical deliberations and mind games. Storytelling, in short, and with a mixed end result. I do like the Butlerian Jihad trilogy, as this introduces some really memorable characters, creatures like Erasmus, the Titan Agamemnon, genius Norma Cenva, and Selim Wormrider. But I do admit, I am rather disappointed in the Hunters/Sandworms story: too farfetched, too inconsistent and as far as I am concerned as uncalled for as for instance the finale of Star Trek:  Enterprise, which I despise. The other books are more of the same: lots of stories set on the various worlds that make up the Dune universe. Quite a nice read and often quite an interesting story as well.

So, extended or not? I am inclined to say "Yes!". But I wish both writers had left Dune's finale alone. As far as I am concerned, Reverend Mother Sheeana, Duncan Idaho and Scytale the last Tleilaxu Master are still wandering the universe in their no-ship, and I have no idea who "Marty" or "Daniel" really are...