The rumored “Gossip Girl” spinoff will be a prequel set in 1980s Los Angeles. The CW has announced that a pilot for a potential series, created by GG executive producers, Josh Schwartz and Stephanie Savage, will focus on Serena’s mom Lily Van Der Woodsen (Kelly Rutherford), as a troubled teenager in L.A. According to an early plot description, we’ll see young Lily move out of her wealthy parents’ home in Montecito to live with her outcast sister in the Valley, where she’ll attend public school and experience the glitz of Hollywood and the excess of the Sunset Strip. Smart move: new town, new era, old music. The pilot (still uncast) will air on May 11 in place of a “Gossip Girl” episode.