Also, considering the revelation concerning the power behind Juugo's abilities and the curse seal, we can state that Sasuke unknowingly has collected plenty of experience absorbing the type of natural energy which needs to be gathered to enter Snake/Dragon Sage mode(and curse seal mode, level 1 and 2), he also is compatible with the mentioned energy and Juugo's flesh.
But again, Tobi did decide to tear out the Kyuubi from Kushina to use it in battle, so might Tobi might have been able to suppress the Kyuubi's chakra in an imagined battle with Kushina, He seems not able to bring Kushina herself under his control as a jinchuurki in complete bijuu mode.
So worst case scenerio for Naruto, is that Sasuke, with this EMS, is able to suppress the Kyuubi's chakra and hinder Naruto from having access to it. But if Naruto were to add the Kyuubi's chakra into his sage energies, and attain a new form, it would be OVERKILL for an EMS Sasuke I believe; and a fitting solution to this dilemma would be Sasuke becoming a Snake/Dragon Sage, therefore amplifying his EMS and putting him on terms with a Kyyubi=Sage Naruto without retaining the ability to suppress the Kyuubi within Naruto. Leaving an awesome fight, to be had by them, and witnessed by us.