This has come up every year since the original WTC attacks. I can't see it myself. There is nothing special about the date other than the obvious anniversary. The original plan was incredibly intricate, and very daring : two planes into WTC 1 and 2, a third into the Pentagon, and a fourth into Washington DC (target unknown?) which failed.

But every year the same fear of an anniversary attack arises, but nothing has happened. Since the authorites will also most likely be thinking the same thing, security will he incredibly heightened. It'd probably be pretty stupid to try a similar thing again.

Of course if something DOES happen, then a big for me too...