The 60-year-old quit the judging panel in 2008 after four years on the programme.
Gary Barlow and Louis Walsh are expected to return, while Mel B has reportedly been drafted in as a replacement for Nicole Scherzinger if the ex Pussycat Doll does not sign.
A spokesman for the X Factor has denied reports that Sharon had already signed a £1.8m deal.
Sharon's husband, rocker Ozzy Osbourne, recently admitted to suffering a drug and alcohol relapse.
The Black Sabbath singer publicly apologised to Sharon and his family for his 'insane behaviour.'