So we learned that you can obtain sage mode from places other than mount myouboku. Orochimaru and Kabuto learned sage mode from a place called Ryuchi. When we last saw sasuke he revived oro, and asked to see the " ones who knew everything." In real life a "sage" is someone who is wise or knows everything. Orochimaru also said to sasuke that he was going to take him to a familiar place. In the time of his training with oro, he could have already been to mount ryuchi.

My predictions.
Sasuke will train with these sages and learn alot of info about everything that has happened since the sage of six paths. I believe he will also learn sage mode.

With these new powers i believe sasuke will come and team with naruto and show the world just how powerful they have become.

In the end however after the threat is over i believe one or two things will happen. (a) sasuke will still hold on to his hatred and will challenge naruto to a fight for Konoha. Both of them seeming to be a type of "child of phrophecy", naruto will be the worlds savior, and sasuke is the worlds destruction.

(b) Sasuke will start to lose his intrest in vengence after the wisdom he gained from the sages. Sasuke however still wants to fight naruto for some mystical reason, like to read each other thoughts thru fist or something like that. This fight will make sasuke lose complete intrest in destruction as naruto has a thing about changing people.....

Either way in the end I believe Naruto and Sasuke will finally be able to fight on truly equal terms, from Genin ninja to sages.