The 22-year-old made 14 appearances for the Bluebirds, who won promotion from the Championship last term, during a loan spell in the second half of the season.
Recent media reports suggested that Cardiff had agreed a loan deal in principle with Liverpool over the Serbia international.
Speaking after Monday's 6-0 friendly win over Tavistock, however, Warnock confirmed that no progress had been made over Grujic's return to the Cardiff City Stadium.
"No updates, not really," the Bluebirds boss told Wales Online.
"I think his agent – as they do – thinks he can try and make more money somewhere else but Liverpool want him to come and I think it'll be good for him. We'll have to see how it develops. But we won't wait forever."
Cardiff get their Premier League campaign underway against Bournemouth on August 11.