It's been a few years since Royal Caribbean had a cruise ship on the west coast of the United States but there may be indications Royal Caribbean plans on returning in the coming years.
According to the Port of Los Angeles cruie ship schedule web site, Jewel of the Seas will be making stops there in September and October 2015. It isn't clear if the cruise will begin and end in Los Angeles, but for at least 3 weeks the Royal Caribbean ship is on the schedule.
Royal Caribbean has not made any announcement about returning to Los Angeles, but in the past port schedules have been good indicators of what Royal Caribbean intends to do.
Royal Caribbean hasn't had a cruise ship based out of Los Angeles since 2010 when Mariner of the Seas left due to violence in Mexico.