When Ronan O’Gara arrives into the Aviva Stadium this afternoon, he’ll sit in the opposition coaching box, plotting La Rochelle’s latest quest to get one over Leinster. But the question is whether, in a couple of years, O’Gara could be sitting in the home coaching box. For Ireland? Or even for Leinster? The contracts of Andy Farrell and his team of assistants end after the Rugby World Cup. Leo Cullen, Jacques Nienaber, Tyler Bleyendaal, Robin McBryde (all Leinster), Stuart Lancaster (Connacht) and Mike Prendergast (Munster) are all out of contract too. These are most of Irish rugby’s main coaching positions, all…