It always makes me sad when a manga reader says "oh boy, shit just hit the fan, the series must be ending". Not only are they being short sighted, the mere thought of it ending is like imagining the end infinity.
Completely understand that, it will start going down as soon as Kishi runs out of Naruto lore (Sasuke, Uchihas, tailed monsters, etc...). Although, I wouldn't mind if he started doing spin off series of it, there's so much to explore in that universe.