I think everyone involved knows better than to even ask him at this point. He doesn't acknowledge it as his own movie. The chapter on Dune in his authorized biography/semi-autobiography is very thin and mostly recycled from info he gave in old interviews years ago.
Arrow hasn't officially announced Dune yet, but they included a postcard with artwork from the film in with some other recent releases, which is their typical method of hinting at titles in the works. Also, Ballyhoo Motion Pictures recently tweeted this:
That's artwork from one of the matte...