Wind element giant ball rasengan that would be so powerful maybe strong enough to wipe out a hidden Village... but how will he be able to stop the damage caused to him... the more powerful he would make it the more damage it would cause him...Maybe with Sage mode, or later possibly a safe way of going kyuubi, naruto would be able to safely use it.
What I would like to see is him learning more Wind jutsu and give Rasengan a brake... Maybe a Sonic boom wind blade which he can throw...That would be awesome, I think naruto is actually working on a similar Jutsu.
More defensive Jutsus like a Body Rasengan... where Naruto would be in the middle of the rasengan and it covered his whole body... like a force field...Naa, maybe something similer to rasengan, but an actual rasengan would like mess up his body soo much.
Exploding Shadow clones... Shadow clones appear with battle axes and katana's... Shadow clones with weapons... Shadow cone appears with rasengan already formed that would be the coolest... Imagine a mass shadow clone jutsu with them all having Rasengan already formed...Yes that would be awesome, the exploding shadow clone idea gives me the idea which I actually already had and lots of other people probably also had, but covering the shadowclone with LOTS OF POWERFULL EXPLOSIVES(paper bombs etc) then just sending them up to the opponent and like having them explode lol, while the real one just stays back and isn't even touched
Maybe another element... Water... He could use wind or water to push the Wind rasengan forward so he want be touching it when it hits the target...naaa I don't really want naruto to have a second element, I just want him to like become super awesome at wind element, and at chakra manipulation techniques(as well as tech like kyuubi, sage mode, shadow clone, and summonings) although it would be awesome, I just prefer if he didn't