Well that doesn't mean to say that Air Canada Rouge wouldn't consider YVR. In fact the north west is a total blank spot for DUB, so I suspect SEA or YVR are probably quite high on the agenda. So too would be the southern DFW, though.
I think that there would be very few opportunities left now out of DUB (apart from increased frequencies perhaps) to the eastern part of North America, because most important points in the east are covered. The only one that's really missing a decent service I'd say is YUL.