Yep, absolute void of any post-release content or even support (like pretty demanded companion-app) is very disappointing. Especially for such a great, big board game, based on a strong franchise, which has so much content to be added to it's adaptation. I sincerely hope, that release of the sequel to the video game would be a great enough motive for FFG to make a full scale expansion to board game. Chrissr09 provided a great idea, that FFG could release a small expansion, like with currently missing bits from original video game, even with scaled up price, to analyze demand and then calculate printing numbers (or even reject the idea, dependent on results) for full scale expansion.
P.S. Interestingly enough, there is upcoming (pretty late) localization of DOOM SE in Russia, which is set for release in 2019. I do believe, that if all plans to support DOOM are scrapped by FFG, then russian partners wouldn't be releasing already doomed (🕶️) game. At least, that fact inspires some hope for future announcements from FFG relating DOOM Board Game.