A shout from his(her?) hand? Yeah right.
I might be wrong about it specifically being a dragonshout, but it most definitely wouldnt be a combo spell if there is a chance that might not be ingame, since the trailer is supposedly gameplay realistic.
Edit: Although one thing I just thought about is that Todd might be half-lying when he says they are only thinking about implementing certain things (for all we know they
are going to be ingame, but they want to keep us wondering)