Deputy state coroner Harriet Grahame will oversee the proceedings in Sydney from October 6 with four days of hearings.

The inquest is examining how William vanished from his foster grandparents' home at Kendall in September 2014.

The inquiry was adjourned in March because of the coronavirus.

Several witnesses are still to give evidence and investigators are examining fresh leads.

Counsel assisting the coroner, Gerard Craddock SC, told a directions hearing in June that there were people who had information about William's disappearance and suspected death who should contact NSW Police.

Six years on and the pain felt by William's family is still raw.

"Time doesn't heal all wounds. William's disappearance has left a significant hole in our family's life - one that will never be filled with wounds still raw until we know where he is and what happened to him," the family said on the sixth anniversary of William's disappearance in Sepetember.

"We live constantly day-by-day in the hope of finding William; hoping to bring him home to put an end to the nightmare for everyone after what has been a tortuous six years.

"Our family will always think of William as a beautiful, wonderful little boy filled with fun and laughter. Until we bring him home, we will remember William with loving thoughts of how he lived, not thoughts of how and why he disappeared.

"We will never give up on William... never."

A $1 million reward for information leading to the return or recovery of William remains open. It is one of the largest rewards on offer for a missing person in NSW.

Anyone with information is urged to call Crime Stoppers on 1800 333 000.