Terrorism will go on for most of our lifetimes, but it remains to be seen if we have the stomach to continue to fight against it long term. It's only been 3 years, terrific progress has been made (albeit not regularly reported) and we have many in our nation, including elected leaders, who want to get out.
Someday we might have a President like Clinton who pursues policy based on polls and survey groups and not on principle, we'll unilaterally disarm and the terrorists will reemerge unchecked their pre-2001 strength.
Then we might have to start this cycle all over again.