A conference in Kilkenny this weekend has been debating that very question, according to an article (subscription required) in today's Irish Times. Dr John Sweeney of the Irish Climate Analysis and Research Unit at NUI Maynooth reported that:
Other crops, though, will thrive as Ireland becomes hotter and wetter. Barley and wheat will thrive west of the Shannon in the moist conditions. Maize will prosper throughout the country.

As I noted in the previous post anyway, Irish whiskey can be legally made without Irish cereals, if that ever becomes necessary.