I agree with the above statements regarding
remote controlled passenger planes. I do believe that sooner rather than later
remote piloted cargo planes will likely become prevelant.
(http://www.dsto.defence.gov.au/globalhawk/coverage/gb230401.html)
This week's events will likely play a large part in the adoption of drones for cargo flights. With no pilots, no passengers, and no human interaction, as long as you have sufficiently strong encryption and a signal strength capable of punching through any possible interception, drone flight is relatively free of the risks now apparent in having tubes of jet fuel flying through the air.
However, I don't feel that the "Bulkhead" option is likely to be adopted either. It has been my understanding that one of the things that allows cockpit crews and flight attendents to remain sane in what is one of the most insane working environments possible. The interaction between the cockpit crews and the flight crews is a major reason why I don't see the bulkhead being implemented.
As for possible engineering solutions to what is essentially a sociological problem, I forsee bulking up of the cabin door, possibly the creation of "security bulkheads" like you see in prisons, where unmovable doors can be dropped in tense situations to partition up the aircraft. (Cutting off terrorists from each other and hopefully, from passengers and pilots.)
One of the other things I have heard discussed is a "DeadMan's Switch". As it's been mentioned before, most planes are flown by wire at this point. Something I've heard discussed is the ability to drop the plane into an unalterable flight path. This flight path would remove the ability of the pilots to actually fly the plane, and thus defuse possible demands potential terrorists would place on the pilots. This last ditch flight path would set the plane on a flight path to the nearest available airport, only returning control to the pilots when it was time to land.