I think due to the news coverage of the case and the people all over the country who were affected, they will have to release information on motive, background, and all that just for closure. They did in the Danforth Ave shooting for exactly that reason and the affected people said that it was cathartic for them to know more information about why this happened. Also right after their bodies were found, the RCMP talked about how they were employing behavioral specialists to try to find the motive. I doubt they would mention that to the public if they weren't planning to release those findings.
I think we will know: motive, whether it was premeditated or not, warning signs and events leading up to the murders if there were any, possible diagnoses that could have contributed, where the guns came from, their best estimated route, forensics related to the murders, witness sightings, general details of the autopsy report, and general details of the goodbye message and any other messages they might have recorded (I'm hoping for a transcript but who knows).
Also I bet anything that isn't in the report, will all come out on some Fifth Estate documentary in a year or two anyway.