As of November 2011, in the New York Designated Market Area, the wired cable and Alternate Delivery System, like satellite, market penetration was 96.6%. That means only 3.4% of the potential audience was watching the over-the-air signals in the entire New York TV market.
http://admin.tvb.org/iframe/dma/Cable_and_ADS_Penetration_by_DMA.asp?sortby=DMAWiredCable -Source
So, the questions for the bean counters when considering the value of the move is: How much can a Freedom Tower location improve the signal to that 3.4%, when compared to the ESB and can any improvement be justified on a cost effective basis?
Yes, those buildings the size of the ESB are planned, but won't be built until the office real estate market recovers in Manhattan, and that recovery could be many years away. The Freedom Tower itself will contribute to an oversupply of available office space that will further delay them.
No doubt, the broadcast consultant engineers have some idea of what those planned buildings will do to their OTA signals, but they will also have plenty of notice before those new buildings reach threatening heights. They will have enough time to move their transmitters if they have to. In the meantime, they can continue to use the fairly new digital facilities at the ESB, and install whatever is then state-of-the-art equipment if they are ever forced to move.
And when it comes to the "internet TV watchers," like me, at some point the cable companies will figure out a way to bring them back to being regular cable customers, even if it means charging for internet-TV bandwidth usage, and making regular cable cheaper. They are not going to let the younger generation stop the lifetime money flow that they expect to help them remain profitable and to amortize the huge investment they have in cables and other infrastructure.