Anime series don't last the same as their manga.

A good example is Inuyasha - the manga is still running and yet the anime and the movies have ended already.

So naruto might end after 230 episodes (which is a lot anyway) or keep on running, that'll depend on how popular it is in Japan. The manga, however, doesn't need to end at the same time.

If you ask me the manga still has ways to go, and it's too popular amoung Shounen Jump readers for it to be pulled out. At worst Kishimoto will receive less money and support and then we'd have the same story but with bad art.

Like HunterXHunter! (yes, I'm looking at you Uchiha Barles!)

So I would stop worrying if I were you. There are too many things left to be solved - mainly Sasuke's vengance, and that should take at least a yea, flashbacks included. Then there's the Akatsuki. And new characters whose origins and personal problems have yet to be addresed. Even if Kishimoto decided to end it now without explaining Sai's past or without fully using all of the Akatsuki members he'd take at least a year and a half to finish things off.