" I don't know about the anime, but if you read the manga then it's readily obvious at this point that it's coming to an end. Naruto's mastered the Kyuubi, the final member of Akatsuki is leading a world war, there are only two jinchuriki left (including Naruto)... Most of the plot threads are beginning to get tied up, this arc is going to last a long time, but it's the last arc. "I think Naruto still has to become Hokage...
It's a general rule that you should always leave the audience wanting more. Too many manga publishers forget this and continue a series long after its welcome has worn off.
I agree with the folks that said the best place to end it would be after this arc. Unless Kishimoto has something really good up his sleeve to extend it further, things should be winding down. This is the perfect time for Naruto (which is the best anime I've seen) to end.
That said, the Naruto universe is very rich. It need not die with Naruto. I think there's plenty of room for new stories in the same universe, following other characters. That said, as long as he's been doing Naruto, I suspect Kishimoto may be ready to try something new.
Please see Naruto Manga to End in 5 Weeks.