Terminal 2 and the Queens Building will be demolished to make space for a brand new terminal complex which will equal Terminal 5's features and also make the Central Area more modern to pax and Airlines operating from there
Though this means the now dormant spectators facilities gone for ever (i doubt it would ever re open sadly), it will be a good face lift for Heathrow
Theres a link and photos on www.baa.co.uk/heathrow Look up the news section and you will get photos of the planned construction, estimated to be around £1.5 Billion
Airliners Net magazine has more details on it aswell, it will be very good for Heathrow as many visitors think the existing Terminals look very old fashioned, which is why BAA is looking on how to change this :D