The existing planning permission was for a 300m extension to the North end of the main runway, but only 140m was built, I believe because of financial considerations: a longer extension would have required massive, expensive earthworks to surrounding areas.
The master plan does indicate a southerly extension which may or may not be built in the future. An earlier White Paper stated that this would also be around 300m, but the new master plan has watered this down to say that it depends on future aircraft requirements and is dependant on purchasing extra land from the cricket club.
Unfortunately AIA cannot afford a "build it and they will come" policy!