Speaking of temporary power ups, Obito's mentioning of his present to Kakashi being temporary leads me to believe that Naruto and Sasuke's powers from Hagoromo too are merely temporary. Think about it; the method in which Obito gave Kakashi power and Hagoromo gave Naruto and Sasuke power is very similiar. This theory can be further supported by the fact that, in The Last Movie trailer, we see that Naruto has wrapped one of his hands in bandages, the same hand that has his Sun Seal. This is most likely to prevent viewers from knowing whether Naruto loses his powers or not, but seeing as how his other hand has no bandages on it, it would seem like he does. Further more, Hagoromo makes mention of how he never wished for the Rennigan to be reborn into the world again, yet here we have him handing it to Sasuke free of charge. This is a very contradictory statement... unless of course, the Rennigan Sasuke was given is temporary.
This might mean that, at some point in time in the near future, Naruto, Sasuke, and Kakashi will lose their powers and Naruto will revert back to Bijuu Naruto, Sasuke back to EMS Sasuke, and Kakashi to Sharingone Kakashi. I believe they will lose these power ups after dealing with Kaguya, and from there, they will return to the Hidden Leaf, where Kakashi will receive the title of 6th Hokage
In fact, this whole ordeal with Kakashi being Hokage before Naruto, Naruto and Sasuke losing their OP powers, and The Last Movie/New Era Project talk may very well give way to part III, the hints are just pointing in that direction more and more.