There will always be a risk, no matter what you do. The question is whether the benefits of air travel outway the risk of travel. Not just against terrorism but any accident.
This is the first time this has happened in 100 years of aviation. That is acceptable, as long is it does not become a regular occurrence.
More viable would be to restrain the passengers, like in a roller coaster ride (this would also add to their safety!) and allowing them to get up in a controlled fashion as the need arises (ie toilet stop or stretching). This way, flight crew could ensure that 5 hyjackers could not get up at the same time and storm the plane!!
This concept may take time for some people to absorb, but it is the most viable and in many ways pratical.