T7 at JFK can't take one A380 never mind two. The A380 is a very hard aeroplane to fill and it needs to be as full as possible to pay as Air France keep finding out. The "halo" effect is overstated I think, it's no more a halo than a B747 over a B777 IMHO.
BA only have 12 of them with no more on order so no plans for JFK in the near term.