I think there's an even possibility of either things happen. I have no doubt that they have something they COULD show, because I remember hearing from someone, perhaps Miyamoto or Iwata himself, that they had someing for E3, but they didn't believe it was perfect. With this extra time, I'm positive that they're ready.
However, Iwata is making another keynote speech, and I doubt it will be entirely about the Revolution. Iwata wants to say something, otherwise he wouldn't be at TGS, which is unusual for Nintendo. What he wants to say may not be about the Rev specifically.. If the Rev is going to detract from his main point, than they may not show it.