Despite police being called within the hour, hundreds of persons of interest being investigated, dozens of searches being carried out and stacks of evidence documented, no trace of the boy - last seen wearing a Spider-Man suit - has been found.

An inquest that began in March 2019 and was adjourned in October 2020 will hold another round of hearings in November and December 2024, NSW deputy state coroner Harriet Grahame confirmed. 

At a directions hearing on Friday, counsel assisting Gerard Craddock SC said he was waiting for an update on a police brief provided to the Director of Public Prosecutions on possible charges against William's foster mother. 

He was waiting for a statement from the officer in charge of the investigation about steps taken since the adjournment in 2020. 

Ms Grahame said she was unable to proceed with the inquest until those issues were finalised.

The foster mother, who cannot be identified for legal reasons, has always denied having anything to do with William's disappearance.

Mr Craddock said a full list of issues and witnesses was yet to be confirmed, but NSW Police procedures on missing children were likely to be probed at the end-of-year hearings.

"We intend to look at whether the standard operating procedures in relation to missing children are best practice as they have developed subsequent to 2014," he said.

"That is not to suggest that anything that was done on September 12, 2014, or the period afterwards, was in any way in breach of any procedures that existed then.

"It's more a question of whether (police procedures) presently are best suited as they can be."

The coroner was due to hand down her long-awaited findings in June 2021, but the date was pushed back to allow various parties' lawyers more time to file submissions.

In November that year, police launched a fresh, month-long search for William's remains, which concluded without any obvious breakthroughs.

A $1 million reward for information on the case still stands.