I've given up on the idea that anything will be exposed to the general public. Will we have proof? Eventually. Right now we say we know, but it wouldn't hold up with intense interrogation. I think it all goes back to the choice to know. People are happy with their movies. If life gets easier for them, they don't necessarily need to know how or why. They just know it gets easier.
Something like Benghazi might eventually be proven publicly, but there's way too much to unwind for the public to acknowledge 9/11 as anything but a terrorist plot.
You know what? It was an act of terrorism. Doesn't really matter who perpetrated it. As long as they are dismantled in a way that they can't do it again. At least for a few generations.