I don't think we will see any changes for some considerable time.
Most likely soon will be a modification to current Hi-jack SOP's whereby the current rules apply unless and until the first attempt is made to remove a pilot from the seat - then its extinguisher and CSD time.
I don't see the relevance of flightdeck visits or door locking when the door is still fragile.
Let us recall that in the WTC incident the terrorists did not sneak anything on board other than a male wash kit. All the gate security in the world would fail.
Weapons on board can be manufactured and lets face it - 3 fit strong blokes snapping the cabin crew necks is no different than stabbing or slotting their throats. So, you cannot stop the people nor the means from being on board.
That only really leaves the flightdeck door. I can't see a worldwide fleet modification being ordered due to cost and practicality. On the smaller jets - lets say a common Embraer 145 - there simply will not be the space to install a new wall, galley and toilet. If you don't modify EVERY jet then the all you are doing is making the few remaining in the old format extremely tempting targets - thus people will not fly on them, nor indeed, pilot them.
I think a better short term and feasible move would be:
1) Improve cockpit security by beefing up the current doors and intalling cctv of the cabin.
2) Improve mandatory comms on board so continuous digital flightdeck audio is gauranteed on open mike to airline ops.
3) Utilise current air defence assets to ensure domestic 24/7 CAP with standing orders allowing downing of airliners.
The combination of 1,2&3 should allow a reasonably confident decision to be made that the aircraft is now hostile. It can be shot down. No target is hit. It would be therefore better to use a bomb on board as is the case now.
The madatory upgrade in comms can be used to install new efficiencies such as radios you can't cross on, ACARS, in flight medical relay, pax communications/email/web, ATC clearances et al.
At least this way 'we' benefit operationally from the cost.
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