The airport has a planning limit of 18 million so will need a planning application to allow 21 million. Luton is in the unique position that its local council will fully support any expansion plans. Talk of another apron and changes to the terminal again with a bit of mini infilling on a much smaller scale. Maybe all the seating will be removed this time and will operate like Thamelink trains in the rush hour with standing room only?
The likely location for another apron would be the existing temporary drop off area with nose in stands facing the multistory. The only uncertainty is will if be connected to pier B via another pier. If it is will that pier then be extended to the south stands? Seems a logical thing to do but it would be a long walk.