This is still an active unsolved case being investigated by EPS.
As of April 2008, the police commission report stated Nancy's name and case as unsolved. The link is above.
For sure the family can call EPS and ask for an update. Print the document out and show the police that the case is still unsolved, it is active and you want answers, an interview, anyone who knew Nancy at the time of her disappearance can re-submit statements. Maybe, since all the time has passed, people will remember more details, or remember something that might have seemed strange at the time but hadn't thought about things in years. Certainly, some things will be forgotten, but people can remember, even after a long time.
I hope Nancy's case is solved soon.
In response to the recovery locations, the changing locations, if we thing in terms of geographical profiling, the changing locations may mean the killer moves around some, living in different areas of the city, thereby creating new hot zones and new direct lines out of the city.
For instance, Nancy was found in a rapeseed field at 162ave and 82street. In 1981 that was a farmers field - but now it is all developed. So at the time, it was 50 blocks from 82 street and 118 ave, which is a current location, close to where many current missing and murdered women were seen, hung out or worked.
In 1981, maybe the killer lived in the 82 str and 118 ave area. Does any family member remember where in the city of Edmonton Nancy Gladue was living when she was murdered?