National police spokesperson Colonel Katlego Mogale said this week no arrests had been made in connection with the killing.
Hettema was gunned down on 29 June 2016.
Two men tied up his wife Elsa and shoved a worker into a cupboard. Both survived the attack.
The men then took off with a cellphone, laptop and some jewellery.
“Investigations are still ongoing and we are still following leads,” said Mogale.
She said police would not rest until the perpetrators were brought to book.
As a rally driver, Hettema won the South African National Rally Championship five times.
He competed in three events at the 1956 summer Olympics as a cyclist and was honoured with a lifetime achievement award by Motorsport SA in 2003.
A Benoni museum has been named after the sporting legend to commemorate his death.
He died at the age of 83.
Source and image: Rekord East