could be i just think it would be cool if learned another regardless the one that he learnsi have a weird feeling that it will be earth, just a feeling
is that why he asked yamato if he could develop a water affinity during thier rasenshuriken trainingi remember watching an anime filler when the pervy sage was teaching naruto to combin his nature with one of the toads water nature and he told naruto because he has a wind affinity he sould also have a good afinity for watter
i doubt he can get lighting nature but it can happeni want him to get lightning and add it to rasengan
if you have more than one element, they usually compliment each other. wind and lightning dont mix so its not likelyi want him to get lightning and add it to rasengan
Water should be his second elemental affinity because he's maternally from the Land of Whirlpools.Stated the obvious.