In either case, it's the only 'true' way the manga can end. With no Ninja System, Sasuke can't become Hokage, but he can become 'acknowledged'. That's the problem with stories like this - the ending is painfully apparent, even if the hows and whys toward it aren't known. Kakishi, for example, may well help Naruto obtain the Rinnegan by getting Obito's eye, teleporting out of the false dimension (leaving Obito trapped but alive) and giving Naruto both his Sharingan and Obito's. Because he still has his right eye, he'll still be able to see and fight. The specific criteria for the Rinnegan are unexplained, but I have a good idea why - either Sasuke will have to give up his Sharingan for Naruto to get the Rinnegan, or Hinata will have to lose her Byakugan, or neither, and that Naruto simply comes near death with the Sharingan in his eyes and is thus saved by the offer of Kakishi and Obito / Sasuke.
But that's the interesting thing about stories. The hows, whys and the buildup to what is often an obvious ending, unless there's a plot twist that Kishi has yet to throw in, which is likely. It's why we read, it's why we write, it's why we love stories.
And why Naruto's the most popular manga out there, for good reason!