Lipinski to retire. Son to replace. But what about a special election?

The Trib reports that Lipinski is set to announce his retirement Friday and that the Dem committeemen are scheduled to pick his son to replace him. But a state statute calls for special elections to fill vacancies in the congressional delegation. Remember JJJ won a special election in 1995 when Mel Reynolds was convicted? So why wouldn't we hold a special election now?