From a New York Times article, headlined City and State Brace for Greater Demands on Diminishing Resources:
With the prospect of Lehman’s space going on the market, the likely result will be a drop in rents at some of the city’s premier buildings and fewer new towers going up, said real estate executives, urban planners and government officials. Those that are built will probably be smaller, they said.
...The crisis on Wall Street does not bode well for the proposed towers designed for financial firms at some of the city’s most important projects, either, including the rail yards on the West Side of Manhattan.
A tougher market for financing
There also may be trouble getting financing in general. From AM NY:
If the housing market softens, developers may get jittery and be less willing to finance all the new buildings going up, leading to lots of empty lots. And big projects like the new World Trade Center and the Atlantic Yards could grind to a halt, according to Chris Jones, a researcher at the Regional Plan Association, should financing becomes more difficult and tax revenues dry up.