I think that they have pretty much told us that New York is their top priority. I doubt they want to blow up D.C. because they want to plant the Islamic flag on the White House. However, I'm sure that SF, LV, LA would be very satisfying to them as well.
I have no doubt plans are being made to turn a merchant ship into a delivery system for a nuclear weapon. At some point that ship will go into a yard and a group will install a bomb in a location that is sealed and unknown to the crew.
After the yard work the ship will go on its way transversing the oceans. At some point it will take on cargo for New York. the operator won’t do anything to raise suspicions. By the time it reaches NYC and diverts into the Hudson River it will be too late. The resulting blast will devastate NYC. The economic impact will be off the scale. Obama is an idiot if he thinks we can absorb that. We’re on shaky ground already.