EI actually has five 320s on order, one due in June and the other four, from late 2010 to early 2011.
Aer Lingus
Depending on the performance of certain routes, it's quite possible that some acft may be transferred from other bases. That said, if a need is identified for more acft, the current state of the industry means that lessors will probably be willing to do a very good deal for EI.
As to traffic figures, the figures for December should be released in the next fortnight, so that should give us the final figures for the year (since EI has been issuing traffic statistics on a monthly basis for a good while now).