http://www.oneworld.com/ow/news/details?objectID=8613
Aer Lingus' last day in oneworld will be March 31. Oneworld hints that the three new members should be joining around the same time; let's see how close they are able to nail the date.
Upon exiting oneworld, Aer Lingus expects to maintain links with many of the current alliance members. I think it's safe to assume that they will maintain codeshare and FFP agreements with most of the existing partners. All of the technology links are already in place so the cost to maintain is minimal. Aer Lingus may want to emulate RyanAir/easyJet's no connecting traffic model, but the reality is codeshare revenue is hard to say no to!