the big concern that will draw a lot of hubbub is the proximity to the Chrysler Building. I hope they use a design that leans or set backs from 42nd street, to maximize views of Chrysler. Maybe something like the Leadenhall Building in London:
122 Leadenhall Street London by
David Bank, on Flickr
Also, this is a very large building. 2 million SF sounds like a lot, but depending on the footprint, it may not reach supertall territory. Another reason to hope for a setback.
Chrysler Building and Grand Hyatt New York at night by
RJ DiBella, on Flickr