Amid weeks of undying speculation, knowledgable sources indicate that David Lonner is planning to leave his post as co-head of International Creative Management’s motion picture lit department to join arch-rival Creative Artists Agency.ICM insiders say the agency’s management hasyet to release Lonner from his contract, which expires at the end of the year, though the young agent has made clear his intention to leave. Sources say they expect Lonner to join CAA’s motion picture lit department in the near future, but no deal can be made until he is officially cut loose by ICM. Sources say Lonner was asked by his ICM superiors to stay on until the end of the year, which he reportedly does not wish to do. Lonner refused to discuss the matter after repeated calls. His ICM boss, prexy Jim Wiatt, issued a “no comment” as did a CAA official. A number of sources speculated that ICM is reluctant to release such a key agent as Lonner right now while the agency is already in the media spotlight over a deal it’s trying to consummate with InterTalent topper Bill Block and some of his partners and associates (Daily Variety, Oct. 13). Lonner joined ICM six years ago after beginning in the mailroom at the William Morris Agency in 1984 and then becoming a trainee. He moved to ICM in 1986 with his former WMA boss and mentor Alan Berger to work as Berger’s assistant and a couple of months later was promoted to a full-fledged agent in the TV division. A year later, he segued to motion picture lit, where he represents such writers as Jeffrey Abrams (“Regarding Henry,”"Forever Young”), Pete Dexter (“Rush,”"Paris Trout”), Jay McInerney (“Bright Lights, Big City”) and Warren Adler (author of “War of the Roses”) and a stable of young directors including Beeban Kidron (“Used People”), Lili Fini Zanuck (“Rush”) and John Turtletaub (“Three Ninjas”). About eight months ago, Lonner was tapped co-head of the department with Joe Rosenberg, while the unit’s former head, Steve Rabineau, assumed more of overseer’s position. Sources at ICM say while Lonner remains very close to Wiatt and other colleagues, he’s recently grown restless and has been somewhat frustrated by some of the agency’s inner workings.