Not necessarily Dublin only, I have seen no reports stating that EI will start new transatlantic routes from Dublin, they all say from Ireland.
Of course they will mainly if not exclusively Dublin but I certainly would not rule out another Transatlantic route from Shannon or maybe Cork (not BFS)
It's Dublin, even EI would admit that, they are adding 1 A330 next year from DUB and 2 routes. 2 more new (not existing airports served) following from DUB also and you don't believe they would try a new airport from SNN which DUB hasn't got?