Davies served as head writer on the BBC sci-fi drama between 2005 and 2010, but told What's on TV that he is unlikely to contribute a new episode in 2013.
"I think I'd be like the ghost at the feast," he said. "What would I do - turn up and make the tea?"
Davies added: "I have asked current boss Steven Moffat not to tell me what they are planning."
The Welsh writer also insisted that there will be no Doctor Who references in his new CBBC show Wizards Vs Aliens.
"I drew the line at Doctor Who - it would feel like the most awful in-joke!" he explained. "Even though I'd love the Daleks to turn up one day, we couldn't do it. They are separate universes."
Wizards Vs Aliens begins on October 29 on CBBC at 5.15pm.
