The flight deck door has to go.
It causes more problems than it solves now. The fact is a flight deck breech, although a possibility, is unlikely to succeed due to the fact that passengers will not permit it to happen post 9/11.
If I were a terrorist organisation intent on causing harm using aircraft, I can now place a cabin crew member in the flight deck in 3 months at a lot less cost than trying to put a pilot in that position.