Glad to hear there's a lot of support here for Rhys Meyers. I really don't think the fact that he was in "The Tudors" with Cavill would really make much of a difference to the producers if he turns out to be the best actor for the job.
Nolan tapped his "Inception" cast members Tom Hardy and Joseph Gordon-Levitt (and apparently Marion Cotillard too) for "The Dark Knight Rises." And in the first sequel, Heath Ledger's Joker blew up Maggie Gyllenhaal, the sister of his cowboy lover in "Brokeback Mountain." Speaking of which, Liam Neeson (Ra's Al Ghul) and Cillian Murphy (Scarecrow) starred together in "Breakfast on Pluto" after doing "Batman Begins."
And Kevin Spacey (Lex Luthor) and Kate Bosworth (Lois Lane) starred together in three movies in a row, "Beyond the Sea," "Superman Returns" and "21," all back to back. They probably enjoy working together and in fact I remember reading that it was Spacey who recommended Bosworth for the role of Lois Lane.
I think the fact that Rhys Meyers is Irish can only help him seeing as how Nolan seems to prefer classically trained thespians ...