Rasengan ultimate defense
Gotta a feeling Naruto will reinvent the rasengan, he usually does something different with his jutsu when he gets a slightly new powerup like the most anticipated fox+sage mode. eg just when naruto got bm mode naruto did a mini rasengan, naruto got sage mode and naruto threw his wind rasengan. etc..
I thought of a possible way for the rasengan to defend it's user similar to how Sasake covers himself with Amaterasu (blaze release). Lol I know we are all sick of the rasengan variations but you might see this one as a refreshing change.
It will only be possible in sage mode and large amounts of chakra and that goes for all shinobi with the exception of Byakugan users ( I'll elaborate about them later).
Now in true sage mode, I think you all remember when in true sage mode the user is encased in senjutsu chakra like an aura which makes the taijutsu style Frog fu hard to deal with. Basically my idea is since there's sage chakra all around the user he/she could in theory through shape manipulation form a rasengan all around there body the same why they do in the palms. So it would will look like someone inside a rasengan, which could protect Naruto against Amaterasu and maybe Susanoo.
Here's a page showing Naruto covered in sage chakra.
I also think the same thing could be done by Byakugan users as they can release chakra from all their tenketsu at once and surround themselves in chakra. There is already the Eight Trigrams Palms Heavenly Spin technique but I guess in this case the user doesn't have to spin physically.
Here's a page showing Neji's ability to release chakra from all his tenketsu.