Changing sort of cases with recent activities on case dashboard?
I don't think you can do it in the smarty template but since you might want the sorting of similar listings to be consistent anywhere it's used you could just change line 545 in CRM_Case_BAO_Case::getCaseActivityQuery() so that it sorts descending.

      $query .= " ORDER BY case_recent_activity_date ASC ";


becomes

      $query .= " ORDER BY case_recent_activity_date DESC ";


Obviously editing core files directly isn't recommended, but that's where the sorting happens for this.