“American Idol” judge Paula Abdul is on the bubble at the show. Her contract ends after this season, and it remains unclear if she will come back next year.

Abdul, who is widely considered “Idol’s” least harsh judge, was asked by ABC News show “Nightline” whether Kara DioGuardi, who joined the show this season as the new fourth judge, could replace her on the show.

“I don’t think anyone (can),” Abdul told “Nightline,” in an interview airing on Thursday night. ”First of all, Kara says, ‘I could never replace you.’ And I said whenever there is change, it’s not about replacing anybody, it’s about possibly moving on.”

A video clip of the interview can be found at  http://abcnews.go.com/video/playerIndex?id=7392520

So will Abdul move on? She did not say exactly, telling “Nightline” only that she is having more fun on the show this season than ever before. And Abdul said that she and DioGuardi are friends.

Despite that, the two exchanged dueling statements in the media a couple months ago, when Abdul told a celebrity magazine that having four judges instead of three is not the best fit for the show, and DioGuardi responded that she was “disappointed” in the comment.

The four-judge format does not appear to be working perfectly this season. Last Tuesday, a time crunch forced the show’s producers to decree that only two judges would evaluate each performance that night, because the show ran long the week before. So if the show sometimes cannot squeeze in all the judges’ comments – especially the acerbic jibes from alpha judge Simon Cowell that tickle so many viewers – will it continue with four judges next season? And if not, who will go?