The official announcement reads:
Due to the effects of Hurricane Sandy on the NY/NJ/CT region, WWE and WrestleManiaâ€™s host partners in New York and New Jersey have decided to cancel the WrestleMania On-Sale Celebration previously scheduled for Friday, November 9 at Bryant Park in New York City. Our thoughts are with all of those affected by Hurricane Sandy.
A number of events at city parks have been canceled in the last week due to the city being overwhelmed and not being able to clear out debris and damage. With a big Noreaster about to hit the area sometime tomorrow and so many people still in a really bad way, there was just no way WWE could hold the event without some sort of backlash. It's unfortunate, but they made the right call here.