EI "evaluating 15+ new North American routes"
 

Potential expansion plans over the next 4-5 years and beyond with Airbus A321LR ... from the Irish Times

Sounds like the announcement of a beauty contest ala Amazon HQ2, to see which tier 2 US cities will offer the best incentive package for a TATL connection.

Baltimore looks obvious, EI has been there before

Are there even 15 cities of decent size east of Chicago (i.e. the range of the LR). Can't see Indianapolis working

They don't all have to be east of Chicago.

Aer Lingus can also use widebody aircraft to operate to new destinations :D

There are a lot of big cities that could support a 3x or 4x weekly service (similar to how they started and grew BDL), Pittsburgh, Louisville, Baltimore, Cincinnati, Detroit, Columbus, Cleveland, Ottawa, and Quebec are the ones that stand out. If the joint venture is approved I wouldn't be surprised to see Charlotte added (it's shorter than DUB-MSP. Plus I wouldn't rule out relatively small cities that are offering good incentives, I know South Bend Airport is trying to get a transatlantic link, and they've a huge Irish connection with Notre Dame (and a school in Dublin too).

CLT seems like it would be a no-brainer if they codeshare with AA / end up being a OW affiliate.

How about DUB-JAX/FLL/ATL/CLT/RDU/BNA/MEM by operated A321XLR? Will they ever consider it?

Do you think they have enough range from SNN-PHX? Don't they have enough range to reach Phoenix.

Considering the A321XLR is only hypothetical right now it might be better to stick to the potential routings of a plane that actually exists and is ordered by EI first.