Just to pour some water of the fire, of Wizz starting ops from Luton to the USA anytime soon, a few things need to be considered...
Wizz Air are not due to receive the A321neo's until 2019-2024, and seeing the huge demand for the A320neo family aircraft type, I doubt Wizz Air will be able to jump the delivery waiting list.
That then moves us on to their exisiting A321ceo's... The Airbus website states the maximum range of this aircraft type is 3200 miles with a "Typical Seating" of 185 seats, Great Circle Maps states the distance from Luton to New York JFK is 3447 miles.
When you factor in Wizz Air operate their A321's in some of the highest seating configuration on the market, this is going to limit the range further. Also the distance of 3447 miles distance, does not factor in the jet stream, which aircraft fly against when flying west bound and need further range to account for this.
There is a reason why we are not seeing the existing A321ceo's operated by other airlines, currently flying transatlantic. Take for example Aer Lingus currently operate the A321ceo and these are only operated in Europe. The airline chose to lease Boeing 757's from ASL to open some new markets from Dublin, to Hartford, Philadelphia, Newark and Toronto for example, as the existing A321's are not up to the job, they have however ordered A321LRneo's to replace the leased 757's in 2019.
Hopefully Wizz Air will prove me wrong and can operate the routes, but on paper it does not seem to be possible.
Just one final point, Wizz Air have ordered the A321neo which has the range to reach the north east of the USA, but if the airline is serious about flying to the USA, they should be considering the A320LR neo. Which has an even longer range and specifically marketed by Airbus as an aircraft for the transatlantic market and to replace the 757s that currently fly these longer thinner routes.