I don't think that was "gameplay" in the strictest sense, but I can see how the horse-jump-arrow might be a gameplay mechanic if the combat is based around the bow like some have speculated.
Maybe, although Link or whoever the main character is has a sword, it's just not on their person, it's on the horse. So I'm not certain the bow being the only thing on the main character is a sign that the combat will center around it, I was thinking it could be more of a sign that your horse in this game will act as a kind of storage box and the amount of items you carry on yourself into dungeons and caves will be limited.
There was another poster earlier, Oatmeal, who said something similar as well.
That's why the horse in the video is carrying a sword (rather than the main character having it equipped.) along with a shield and I think a couple other things
The combat being centered around the bow would certainly be interesting, but I'm not sure I'd want that, I'm sure they would come up a good execution for it, but I want the game to have both melee combat and long range, assuming they want the bow to be important. I don't want on replace the other.
I know the combat in 3d Zelda games have had their problems, but I would rather Nintendo try to improve on that aspect rather then just throw it out in favor of redesigning the combat around the bow. I'm sure they could make it compelling and it would have an excellent execution, it certainly wouldn't be a deal breaker, it just wouldn't be my preferred option.