^ don't forget that more 'loose ends' can still be created. It's really hard to predict whether a series can end or not. The author or the publisher can choose to continue if they want to. Dragonball for example, the storyline can actually ended cleanly after Piccolo, Freeza, or Cell saga but Toriyama-sensei continued it anyway. (I am actually happy about it) :P
Toriyama wanted to stop twice. First after Frieza and then after Cell and make Gohan the "new hero", passing down the torch so to speak from Goku to Gohan and thus ending Goku and Dragonball's story. Both times his editors forced him to continue as he was bringing in the big cash and had massive popularity. It's called milking the cow. By marketing defintion Dragonball was somewhere between a Star/Cash cow.
In Kishi's case it would make little sense for him to be forced into a "part 3". His main characters have basically become godlike, bringing in even stronger villains out of the blue would not only be highly weird in a "logical" world like Naruto, but also completely break the power levels DBZ style. In Dragonball it was more believeable as the whole universe was included, so Toriyama could easily write in new villains without it being unbelieveable. But in Naruto it would just suck. In a world where information is key to survival it would be weird for a new super-uber villain to suddenly pop out of the blue.... Unless someone pulled a Kabuto but not only absorbs Orochimaru, but Madara, Hashirama, Sasuke and Naruto's DNA as well to become the super android beast of destruction and 9000 power.
So yeah, I think Naruto will end without continuing into a part 3. Hopefully. However that's still long ways off. End of next year
at the earliest.
On another note, hopefully Bleach will pick up the rankings in a couple of weeks. If not then I swear the voters have gone mad. Rate it low, but don't bottom it for no reason.