Mark Frost did an AMA two days ago. Some good info comes from it, including that they tried to bring Chet Desmond back, but "found no easy way to bring him back from wherever he is".
https://www.reddit.com/r/twinpeaks/comments/7bn45h/im_mark_frost_cocreator_of_twin_peaks_and_author/
https://www.reddit.com/r/twinpeaks/comments/7bn45h/im_mark_frost_cocreator_of_twin_peaks_and_author/