You don't need to have an affinity to learn an element, it just makes it more difficult. Most Jounin have at least two elements, and Naruto's training method, with his hundreds of clones, means he can do in weeks or days what they do in years. And now that the 9-tails is his ally he can spam as many clones as he wants to to train anything.
Technically if he wanted to, and had the time Naruto could learn every jutsu that wasn't KG and master it more than anyone else ever has. He could combine them all too, like use raiton armor with sage mode and KM and use a rasenshuriken or something.
If you think about it, right now Naruto's potential is limitless. The only thing holding him back from being the SO6P is not having the rinnegan.