In relation to your 1-3, I think the chances of those things happening are low because (and I'll go by category)
1 - US security has wised up to this, and intelligence resources are at 100%. Chances are the people would be caught in the planning stage. Of course, it is 100% likely someone out there is planning another 9/11, but successfully pulling it off is a long shot
2 - No way. If the terrorists had those weapons they'd have used them already, probably on Israel first. 9/11 was devastating but was relatively low tech. I can't see the terrorists being able to successfuly deploy those weapons, not without a country like Iraq/North Korea helping them. And you can bet Western intelligence is absolutely crawling over those places
3 -Again, like above. I'm sure terrorists might have Nuclear materials, but turning them into a bomb is something entirely different. Possible someone might try a 'dirty bomb', but getting it into the US ain't going to be a piece of cake. I really can't see it happening.
One further prediction -
A nuclear conflict taking place in North Korea within the next 2 years - 90%
It is almost inevitable I'm afraid. If I was Bush and Blair, I'd be going after those mothers first.
I used to think the brain is the most fascinating part of my body. But, hey, who is telling me that?