OK, what are they waiting for then? On 9-11, instead of using planes, they could have driven these nukes they have into the middle of NYC and DC and set them off - without detection. They could have used them to thwart the Afghanistan and Iraq wars, why didn't they?
If indeed something like this ever happened inside the US, it won't be the "traditional" AQ people, the ones who are blowing stuff up with conventional explosives and attacking foreign oil workers in SA - it will be someone else who has done this (China? who knows).
AQ's deeds could be "grey terror", designed to set the stage for spetnaz to do the "real" dirty work at some point. Many at TFP subscribe to this notion as it is how Russia has operated in the past, primarily in Eastern Europe.
I don't really know why AQ would wait. My impression is that they followed that procedure laid out months ago. The warnings, the 8 demands, etc. etc. Then supposedly a final message will serve as the "go" signal.
I know it sounds like I am taking them too literally, but they tend to be very obsessive-compulsive.