Demi Lovato X Factor Judge?

We broke the story, producers are close to sealing a deal with Britney Spears to fill one of the 2 vacant chairs, but that deal is still in negotiations -- it is NOT closed. We're told both sides expect to reach an agreement and if they do Britney will end up with $15 mil for the season.

Lovato certainly has a fiery personality -- as we reported, she once socked a female back-up dancer in the face during the Jonas Brothers tour.