There are actually three A320s coming next year, from what I understand.
I agree that operating overnight routes is a good idea and certainly something that could be tried with some of the proposed new longer routes like Athens, Moscow, Istanbul etc, because you also get the advantage of the time difference. An A320 leave DUB for say DME could leave at about 11pm and be back home at about 8am, in time for a full day's flying.
As for the A321s, the only airlines I'm aware of that are getting rid of them are bmi (some going to Monarch) and SAS, which has never been terribly good at this whole standardisation thingy (the term "smorgasbord" is particularly apt!), but they both have IAE engines. I think the attraction to EI is that this is the only type which could have costs per seat mile which could come anywhere close to FR's 738s, being a 212 seater.