I love the cries of "gimmick!" interspersed with "this is impossibly different for standard game designs!" You can't have it both ways, people.
As for fatigue: believe me, not an issue. Yes, you may perchance burn the odd extra calorie, and we mourn your loss. But most people's wrists can handle hours of writing (it's the fingers that give out) to give one example, and people can play badminton indefinitely even if they haven't played in a year (it's the cardiovascular that gets you.) Did anyone suggest that DK: Jungle Beat would cause fatigue? A lot of the same basic motions. As long as you aren't holding your arm still and unsupported for extended periods, you'll be fine, my dear couch potatoes.
And try playing Zelda and timing how long you actually have to spend continuously swinging a sword. Except for a few special spots, it's not too damn long. Boss battles have you manuevering much more than using your sword, and for the rest your foes are quickly dispatched. So yes, I strongly suspect we will see fighting that involves you swinging, though I doubt it will be the massive gestures shown in the video.