Before adding the stinger: “I think that one day I’ll just wake up and organically it’ll be done. Maybe I won’t wake up and that’s why it’ll be done.”
Sounds like fans should make the most of watching him on the big screen while they still can.
The film is set in 1969 in Hollywood, and follows an alternate timeline that combines "multiple storylines in a modern fairy tale tribute to the final moments of Hollywood's golden age".
Leo's character falls into alcoholism after his career begins to plummet, and is accompanied by his best friend and stunt double Cliff Booth (who is played by Brad).
Once Upon A Time in Hollywood is Tarantino's ninth film, and will be released in Australia on August 15.
PLAY TO WATCH the actors at the premiere