How Imarti died will probably be resolved shortly
However, whether this track was planned or unplanned is another story altogether.
Personally I feel this track was not planned / was thought of a few weeks ago after so many requests for HS backstory.
I think they were going to leave Imarti as a memory and as someone who died during childbirth.
However because viewers wanted to see more depth into HS character and to increase his onscreen time (which I dont mind at all), this whole Imarti death mystery and story was created.
I keep reading about parallels drawn between the relationships of mother -daughter duo and Ashok, and now HS. Well they have a great writing team so its not hard to weave a new story and draw parallels to tracks that happened in the past. Thats what writers do...good writers that is.
Whether it was planned or not does not matter to be honest. I am glad to see more screen time focused on HS because AD is an amazing actor that can simply emote without a word. His eyes and expressions speak volumes and are sometimes better than his classic dialogues (I love when he randomly bursts out into english).