Maybe I missed it in the many, and often rambling, posts, but has anyone addressed why we haven't been attacked again since 9/11? If we're talking about predictions, I would guess there were VERY few of us who would have predicted that on 9/12.
Second, it's remarkable how much confidence people have defining alternative courses of history. (Of course, it's made Harry Turtledove a fortune.) I haven't seen the ability to predict events in advance that would lead to such confidence.
Pretty good summary. Scenario 3 is clearly ludicrous (unless you like totally inconsistent logic and a complete absence of evidence). Beyond that I tend to favor the Occam's Razor solution, which is number 1. I could be wrong, of course, but a plan to have the world's mightiest armed forces hunting you down, killing your followers and forcing you to live in caves hardly seems like one that would have survived the Al Qaeda brainstorming session.
I also have a hypothesis why scenario 1 is never mentioned - and which is consistent with the responses on this board. It would require giving credit to the administration, the most appalling scenario of all!