Friedchicken,
Last I heard from someone who works on the Elmdon side of the airport was that the closest hangar to the old tower is due to be demolished first, but as Getonnit says no date has been mentioned.
The other hangar is slightly newer and some work was done on it by Fly Be so may stay up a bit longer.
Unless they are in a dangerous state of repair doubt they will come down that quickly, unless BHX has a company already lined up that want to use the space left.
This as its very expensive to remove asbestos.
BHX do continue to look for opportunities to make revenue, so perhaps they can pull a rabbit out the hat as they did with the Monarch Hangar.
Nigel