That was my first thought, but I kind of doubt it. At least, I doubt that'll be added to the endless hallway, since the gag was replaced by the now-popular floating candelabra."A footstep (and shadow) effect that Anaheim doesn't have?" What could this be? Is this possibly the original incantation of the Endless Hallway that was intended to feature speakers echoing heavy footsteps down the hall before ending with a rush of cold air blowing into the faces of the doombuggy occupants?
What I think is more likely is this: somewhere in the ride, a video projection of a shadow (a la our attic's phantom pianist) will walk across a room. The floor will be made of a material that can either be sucked downward in footstep shapes, giving the illusion of dirt or the like being compressed by footfalls. Alternatively, the floor could appear to be stepped on by bloody or muddy feet. It'd be a cool effect, and I think it's doable.