Will terrorism become the accepted method of warfare in the future for the disenfranchised and alienated peoples?
What then, is to deter individuals and nations from engaging in this high-profit, low risk warfare?
Can the international community cope with this emerging challenge?
I really doubt it. I don't think most people will buy into the idea of killing innocent non-combatants to achieve political ends. I don't think society could survive if they did. It is a tactic of fringe elements who cannot achieve political power in any other way.
However, the prevalence of terrorism may cause governments to have to change how they behave in order to prevent an escalation in the use of terror to achieve political ends.
I think the argument could be made that you don't have to look to the future to answer your question, terrorism is being used that way TODAY. To be honest, I don't know if there is a way to prevent terrorism. What deterrent will work on someone willing to kill themselves by crashing a plane into a building or detonating a suicide bomb? The guerrilla warfare tactics of the American colonists in the American Revolution were seen as cowardly by the British, but those tactics are still being utilized today.
The most lofty and hopeful deterrent to terrorism is peace. If you can keep people from being alienated and disenfranchised, then they will have no need to enact revenge.
I'm pretty sure it will be. For one thing, it has been what "disenfranchised and alienated peoples" have always done. Second, now more than ever, there is no way that poorer people can have any chance of fighting a conventional war against any serious power. Therefore, any resistance is likely to come in the form of terrorism.