These take years of planning and what was a good idea at the application stages may not be so now.
From Barney's link:
However, it is unclear how quickly the airport will grow. Stansted�s passenger numbers have fallen slightly in the past year to about 22.5 million because of the drop in demand for European budget flights. Ryanair is grounding 16 of its Stansted-based aircraft this winter. The airport will also have a new restriction on the number of private jets that it can accommodate.
Monarch looks on shaky ground, and may be next for the chop.