"Predicting successful terrorist attacks is like predicting earthquakes. It just cannot be done on a reliable basis. (hmmm a dubious comparison...large terrorist organisations, while highly secretive + capricious, are run by people with goals and plans, so gaining inside intelligence on them is much more scientifically possible than the almost complete randomness of earthquakes).
I seriously doubt that any "reputable terrorist organization"* would EVER use WMD in a first-strike. Doing so would cause them to loose public support in the Islamic states and no terrorist organization can function without support from the local population. (moot - depends how vast the resources and reach of the terrorist organisation is. It seems Al Qaeda has so many members and monetary resources it is almost like a nation in itself. It's ultimate goals are outside of the approval of governments so why would it be concerned about losing what it never had? It has never had official diplomatic support and any current support from Islamic states would be completely clandestine anyway. In fact it could be argued that by delivering a 'knock-out punch' to the US by using WMD it could garner even more support in the muslim world than ever before. Eg, do the palestininians hate the PLO because it resorts to indiscriminate bombing of children and women on buses? Did support for Hitler dry up after he started bombing London with V2's ? I doubt support for Al Qaeda would dry up whether they destroyed 300,000 or 3,000? people don't care if they are utterly convinced that the cause is justified. I'd say if Al Q used WMD and killed 10's of thousands or more Americans on US soil it would be like pouring gasoline onto the fire of muslim fanaticism rather than dousing it)
Any state that had anything to do with the terrorist organization would come under intense world pressure to hand over the terrorists... and they WILL hand them over or face severe world sanctions. (It seems apparent that most of Al Qaeda are beyond the reach of governments and their army/police forces. The US and Pakistan would have found Bin Laden and all his cronies by now if Governments could just hand these buggers over any time they want. After all the terrorist actions in Israel does the PLO or Yasser Arafat just hand them over, just like that? Nope....+ they don't give a shit about sanctions. I'd say the same goes if WMD is used by terrorists that some countries may be harbouring.)
Any state that actively participated in the WMD attack would cease to exist 45 minutes after the attack. ( but Al Qaeda are not a 'State' and they operate outside national borders - any support by some Islamic countries is completely clandestine and most likely only in the form of financial support. The US isn't going to nuke other nations on some flimsy notion/evidence that that country has some links with Al Qaeda, especially now that the US has lost all credibility over the farcial claims of WMD in Iraq)