BA have always stated that frequency and flexibility of their JFK route is key. The have also stated the 747 will be the mainstay of this rote until they are all finally retired in the 2020s. The A380s have always been intended to operate on longer range high capacity routes where frequency and timings are not so important. The shorter routes, for example IAD, is made possible by fitting in between rotations so to speak. The A380 is really not the be all and end all of high capacity routes. Other aircraft do still and can do the job very well. Right now the 747 is the perfect fit for BA on the JFK route.