I don't think that there is going to be much going on there. The level of situational awareness for the city is too high.
You can get something small in there, a grenade perhaps, but there is still too much physical separation between the people and where the vehicles can be for an effective detonation of a weapon that is in a vehicle.
My brother is going to the city and will be downtown, and not in Times Square and other than him having more to drink than he should, I'm not overly concerned for his well being.
We will have to see how it comes out. There are greater risks outside of the metro areas than within. The effectiveness of the hit on New York and DC was because of the fact that there was no awareness in the public realm.
Still keeping my fingers crossed.