First, I'd like to see an EXACT quote of the alleged prediction. If he predicted a major terrorist attack somewhere, somehow, someday, it's kind of like predicting that someone, somewhere, someday would eventually win the lottery. It doesn't mean that he has inside knowledge of any sort.
Second, this report is dated 2002. It's now 2004. Nukes are "use it or lose it" in the absence of a large and extensive infrastructure to maintain them. They are complex devices that contain precision electronics, various reactive chemical compounds, and radioactive elements that emit neutrons (which affect the electronics and reactive chemical compounds). They have a finite shelf life--which is much less than a year.
In case you didn't notice, nothing's happened.
Second, al-Qaeda was as successful as they were because they practice very tight OPSEC. When some Islamist start giving all manner of detailed scenarios of how they're going to detonate nukes in the US, it's a sign of the movement's weakness.
They may have 20,000 operatives around the world. But we bagged most of their first-rank people. How do we know this? The bombings in Morocco, Saudi Arabia, and Turkey. They were executed by al-Qaeda operatives. Before we went after al-Qaeda tooth and nail, they had senior operatives whose main job was to keep the young hooligans from doing anything stupid--like annoying their fellow Muslims. Well, they're now doing just that--which is evidence that the "adult supervision" has been eliminated.