Whether it happens in the near future or distant future, courtesy of AQ (a.k.a. 'The Pig Suckers') or some other group, it's likely to happen. There was an episode of the McLaughlin Group (not that I'm a JM viewer anymore) about ten years back; all the conservatives present put the likelihood of nuclear terrorism against the US in the 90%+ range (IIRC), and all of the 'feel-good-liberals' put the likelihood close to zero. As usual, the 'iberals' were completely delusional. Bottom line: it's more difficult to protect a country this size than it is to sneak in a nuclear device, just once. Especially when the federal government is unlikely to say anything, if they stop an attempt at nuclear terrorism (or two, or three, or)...
The problem is, Bush has done a piss poor job of advertising the response that would occur if there ever was a nuclear attack on the US. Obliteration of Tehran, Waziristan and a few other sites ought to be the response, I don’t care who claims responsibility. These jihadis think terror is a one way street and no one has given them any notion otherwise. PC will contribute to the next attack. Our fathers didn’t have any qualms about threatening to kill 100 million people in response to an attack on the US. This generation does, and the result is our potential demise.