Can Naruto create unlimited Rasenshurikens anytime in future?
No, I don't think so. I believe that Kyuubi's chakra isn't unlimited.


   First, Kyuubi cares, that Naruto wastes it's chakra. Second, Hachibi's fight against Sandaime Raikage suggests, that the chakra of a beast isn't unlimited, because Hachibi was knocked out because of exhaustion. Because the beasts are pure chakra, I think that would mean, that it has too less chakra.