EI has reached agreement with Airbus and lessors:
Aer Lingus Group Plc UK Regulatory Announcement: Statement re Long Haul Fleet
Basically, the two oldest aircraft, DUB and JFK, will leave the fleet later this year and March 2010, while a new A333 will be delivered in April. The second new A330 for delivery next year will be delivered in 2013 and the first two A350s will be delivered in 2015.
That said, EI will have the ability to convert orders A330s due for delivery after 2013 to A350s, if it so chooses.