Don't lose heart me hearties, don't blink either cause I have a feelling that this whole thing is leading up to "THAT JUTSU".
What is the connection between Minato, Rasengan, and Naruto? Recall that Jiraiya said that Minato NEVER does anything without a reason. Why did Minato develop Rasengan and then Show it to Jiraiya, Why did Minato ask Jiraiya to be Naruto's God Father?
Answer, Minato had always wanted a family he developed Rasengan to pass on to his Kid/kids. Minato may have wanted his and Kushinas child to inherit the Fox from the start (when Kushina got old). Minato taught it to Jiraiya probably as a precaution, Minato wanted Naruto to complete a Jutsu, but it requires both Rassengan and Fox chakra to do.
My wild guess is that by exploring this avenue, Naruto will discover/develop a new twist to Rassengan. Is this anything but a wild guess, lets wait and see. Let's also wait and see what happens when Sage Mode is put in the mix.