At their current levels, Sasuke doesn't have a chance. Naruto is far too fast and Kurama puts him in a different league than Sasuke.
That being said, Sasuke is due for a power-up, and I am sure that his development will put the two on relatively equal terms. But I think that people are missing the whole underlying premise of Naruto vs. Sasuke. Kishi has indicated throughout the series that their conflict is more philosophical than anything else. Naruto relies on friendship and hard work in order to overcome situations while Sasuke abandons his allies in order to pursue individual strength. I think that this element will play a major role in their upcoming final showdown.
As for the business about Amaterasu, Naruto is far too fast for Amaterasu to be effective if it is used like it was against A. Sasuke has demonstrated other uses for the technique, though. In essence, he has turned Amaterasu into his defensive technique and seems to be making Sasanoo his primary offensive technique. Plus, he has his fire and lightning abilities, which could be upgraded and be more effective in the future. Honestly, I'm not even sure if Amaterasu can burn the Kyuubi Cloak since it is pure chakra. I think the cloak would act much like Gaara's sand in that while individual sections could be burned, but the fact that it is not a singular physical object (like an arm, building, etc.) would likely keep the whole cloak from burning.