Even though everyone knows who killed who, the history lives in paper, not in people's memory. People die and memories fade away. If fact and truth don't get exposed now, it will always be a series of mysteries. So we should demand for the truth and it must be provided.
However, I, personally, think this case will never be opened again. Why would any of the sacked Royals give up their power and property so easily. We haven't heard a single official statement from them yet. They wouldn't care about what people wanted or what the election says. At this point, all they want is an easy escape. The political parties have exchanged the facts of Royal Massacre with the termination of Royal Institution. And the Royals know its the right time for an easy escape. So they did, give up Narayanhiti and the royal status. In return, the real killer will always be in dark shadow.. Political party, especially Maoist, is happy to show off that they kicked out the Royal Institution.
Maoist wouldn't care about the truth either because they want to forget the past as well. They have used the guns and killed thousands of people to get the power too. So the mystery will never be solved unless old Mr Koirala speak out before he die or loose all his memory ( he hasn't got enough time either coz that time is not very far).