To be honest, I don't think that ninjas will be a competitive tribe in modern. Using ninjutsu feels as dangerous as mutating (which as well sees no play in modern afaik).
Kaito himself could be a solid planeswalker for some decks. His +ability generates card quality/advantage, he protects himself with his static and -ability and his ulti seems to be gamewining. And on top of that he is a cmc3 planeswalker which makes him a possible include in modern decks.
But I'm not sure whether he will be enough to make ninjas viable. My guess would be no, but who knows.
Oh and don't get me wrong, I love ninjas as well. Yuriko is my pet commander deck.