The only known person to naturally possess Mokuton is Hashirama. Now the reason for this could well be the fact that he was the reincarnation of Ashura. So, in theory Naruto too should have acquired it with him being the next recincatnation. However, there has been no indication of Naruto ever possessing this ability, so for him to acquire it now would be pretty lame.
However, in my opinion Kishi really does need to tie up these loose ends and give reasons as to why Hashirama had it to begin with, especially when no one else has been mentioned having possessing it, with the exception of raping his cells.
