Handicapping a music director race is always a dicey proposition, since symphony orchestras tend to treat such matters with the secrecy normally reserved for international war plans, but one of the best ways to distinguish the front-runners from the also-rans is to note carefully which conductors keep popping up unexpectedly during the time that the search is ongoing. In Detroit, current conventional wisdom says that 39-year-old Mark Wigglesworth, a talented Briton who has been making the rounds in North America for the last several years, may be high on the DSO’s list to replace Neeme Järvi.