Larry Silverstein, the developer of the World Trade Center, backed off on plans to build perhaps the tallest residential tower in Manhattan at about 1100 feet. The site falls under the Hudson Yards district so it would be have been necessary to build office space as part of the building but the developer was in negotiations with New York City officials to get a variance to build just residential/commercial. The feeling was that the site was closer to Midtown west and it would make more sense as primarily residential. Negotiations were also over the amount of affordable housing that make up part of the building. Apparently, an agreement was reached over the affordable housing component but then Silverstein decided to put the site for sale instead with CBRE.
This makes sense because by the time this property would have gone to the market, it may be too late for the luxury market. Additionally, 40th street and 11th avenue is a location that will probably be more desirable in another 10 years as it becomes more difficult (read impossible) to find sites. This site as a buy/hold would make sense and/or to build rental housing at this time.