BHX's projected 27-32 million traffic figure for 2030s is just to push the planners.
If the airport realy thought that would happen they would be pushing for a 2nd runway. Instead they are goung for a longer runway which implies the owners think it will grow slow but steadly. The master plan has the airport growing at 4.9% each year between 2006 and 2010. 0.9% is well below plan. BHX is treading water.