I can just see it now - New York (Gander) International Airport. More seriously, I've heard rumours on and off about Long Island MacArthur Airport being the "low cost" international New York airport, should any ultra low-cost carriers wish to try introducing such a service to the US. It seems like a perfect Ryanair airport - 44 miles from its intended destination, minimal other users, public transport links (although they don't really provide a great service to the airport itself). Of course, the big barrier is getting Homeland Security to set up an border control there. Anyway, I digress...
737s transatlantic will definitely become more commonplace with the eventual withdrawal of the 757s, which are of course very commonly used for regional UK service to the US courtesy of United Airlines (previously Continental). Should they wish to continue services to Glasgow, Newcastle, Bristol, Belfast etc, then the 737MAX would likely be their first choice. However, Ryanair have been talking about crossing the pond for some time and they haven't managed it as of yet. I do find Ryanair stories fall into two broad categories - true (in which case we see it come to fruition quickly) or nonsense (like the standing seats, pay-as-you-pee toilets, pay-per-view porn) that never really sees the light of day - I strongly suspect that the transatlantic operation is in the latter category.