I was thinking about your question last night.
It seems like they wouldnt risk the heightened awareness
that we naturally have on this date.
Their resources would be better spent on a day we do not expect imo, and that would outweigh any PR of a repeat on the same same.
But they are crazy so who knows.
That's what I think as well.
Something like a truck bomb in a mid-size city would be much more doable than a dramatic 9/11-type attack. One has to wonder whether they will wait to try to top themselves, which would be difficult, or go for the easier targets. I do believe their mindset focuses on specific dates as significant. The 5th anniversary of 9/11 would be one of those days.