Hopefully history wouldn't repeat itself this time, I believe 1.9 would be delivered within the estimated time frame (Q1) as before 1.8D was released, it was announced that the devs may jump to 1.9 directly instead of 1.8B  as they'd already made content and the estimated update would've be bigger than lettered update. 

April - May seems like ideal time frame for Steam release (also reflected on the game's official steam page) 

Yes, I agree with you. A reliable, usable, and available timeframe is necessary. The previous 1.8 release incident was an avoidable and unacceptable regret.