Hauraki District Council is due to release the findings of its internal review next week after an independent review.
Keys' brother, Ian, told the Herald on Sunday he had been briefed on the council's findings.
He "wasn't happy with the result and would be seeking legal action to investigate the matter further".
The council's chief executive, Langley Cavers, said the review recommended how the council could "improve our processes to ensure hazards are identified in a timely manner and dealt with proactively".
He said it was unclear how long the sinkhole had been there before Keys rode into it.
Cavers confirmed council records indicated no other incidents had been brought to their attention, adding it was "not uncommon" for sinkholes to appear. "This was an unfortunate accident," he said.
Ian said his brother had had his fair share of "ups and downs" since the tragedy.
Keys could "blink and talk" but is likely to remain in the spinal unit until mid-January.
Keys heard his neck snap when he was thrown over his handlebars after riding into the sinkhole on October 15.