The end of Manga, with a special chapter "years later".
End of saga, later the manga will continue with new characters and stories.
I think its a bit naive to think Kishimoto cannot produce another manga or w/e while continuing Naruto...at this point he must have a lot of writers and interns working for him.
And about the reappearance of Orochimaru. Remember the fights Sasuke had with Itachi? Orochimaru said Hi and was wiped off the screen again. He should be happy if he gets even one more chapter.
The fact that Orochimaru was resurrect, to me, shows that this manga is far from completed.
I thought that it was pretty much done, but now I think that after the 4th great war arc, we will have another long arc.
Tobi will be defeated here, but not Madara.
And Madara will become the big boss.
Eventually, Naruto and Sasuke will fight and Naruto will win.
And then, it will be Naruto and Sasuke vs Madara.
That's my guess, anyway...