Norwegian are interested in attacking current markets, of course the exception is Cork for obivous reasons (political bait).
United have not only cut Belfast, they've made several cuts in the UK including cutting Newcastle completely.
Let the economy and currency settle first, I've no doubt that Belfast will not see a Transatlantic service in 2017.
Maybe again once the A320 NEO family and the 737 MAX become widespread. When this happens I can see more than just New York being added.