Orchestras in New York and L.A. may have made big splashes in recent weeks with music director announcements, but the Philadelphia Orchestra won’t be rushing to find a replacement for the soon-to-depart Christoph Eschenbach. “A search committee will be in place by the time of the orchestra’s annual meeting in September. The committee, whose work may take several years,” will canvas the entire orchestra as they work, and those in charge insist that the process will not be truncated to insure a quick succession.