Board Thread:Theories and Speculation/@comment-5012682-20150620162706/@comment-26545929-20150630062814

I think its the case that all shinobi can learn all the five of the basic chakra natures such as when the entire Allied Shinobi Forces were able to create a basic mud wall after learning the hand signs. It's just people like Sauske and Boruto and all other shinobi are predisposed to 1 or more natures which allows them to use more advanced jutsus of that particular nature whereas they couldn't with the other natures not having a natural "affinity" with it.