Re: Sage Mode vs Sharingan
Sage Mode is great, and yes, recent release of the manga does not contain any clue whether the Sage Mode can be upgraded to another level.
In Sage Mode, Naruto needs on to balance his chakra with the natural energy he gathered. But under this mode, Naruto can only use two(2) Rasenshuriken on each Sage Mode. After that he will return to his normal form. Even when Naruto comes face to face with Nagato, he's been able to resist Nagato's control, not merely in Sage Mode, but together with the Kyubi's influence.
NarutoBase.net - Naruto Manga Chapter 444 - Page 4
If Naruto won't use the Rasenshusiken and stay only in Sage Mode, I don't think he will win against the Susanoo or even to what the EMS packaged ability.
I'm sorry to say that EMS also consumed chakras. But on the other hand, with Sasuke's intense feelings of hatred, he's been able to develop it and make it become more powerful. If I remembered it correctly, Sasuke's Susanoo is in a point of transformation when it was interrupted due to the limitation of the MS eye. And that's when Sakura, Kakashi & Sasuke been reunited.
NarutoBase.net - Naruto Manga Chapter 484 - Page 9
And still, there are some Sharingan Jutsu that Sasuke's not been using but already been revealed in the manga. Like the Izanagi & Kamui.
And for Naruto, what he have lately is only the Fox Chakra and I don't think it counts as a Natural Energy. And if Naruto learned to efficiently use this new power to create another new jutsu, I don't think it will be considered as a Sage Technique under Sage Mode. Maybe under Kyubi Mode or Fox Mode perhaps or a collaboration jutsu between Sage & Kyubi Mode.
Also, I don't think Naruto will let the frogs to help him during battle with Sasuke. Unless Sasuke has gone wild destroying everything or even killing whoever he sees friend or foe. The battle will be a one on one, or may I say Sasuke against Naruto (with a little bit of Kyubi's Power & Itachi's gift).
He wanted to bring Sasuke back but never wanted to kill him and definitely doesn't want to loose against him. That's why the upcoming battle between the two will become very difficult for Naruto.