My big concern with Naruto is the story pacing. Since the start of the series, how many arcs have there been? Zabusa, Chuunin exams, Akatsuki shows up, Tsunade becomes Hokage, and Sasuke runs away - that's part one. And that's 240 chapters. Between Sasuke getting the curse seal and him deciding that he was going to join Orochimaru we've probably got about a two year span in publishing. Plot-wise, in that time, we had Sasuke learn Chidori, Jiraiya be introduced and teach Naruto to summon frogs and about Kyuubi, Orochimaru fight the Third, Naruto fight Gaara, Akatsuki be introduced, Tsunade be introduced, Naruto learn Rasengan, Orochimaru try to get his arms healed, and Sasuke and Naruto decide to fight. Half of that is incidental details to the plot that could've been done easily otherwise (i.e., Chidori, Rasengan, and the frogs are simply techniques, Gaara's craziness was just an excuse for him to become Naruto's friend, and Orochimaru's loss of his arms and subsequent healing was just an excuse to introduce Tsunade). The first major plot arc laid out was the Sasuke revenge arc, and in terms of direct action on that we've had one encounter between Sasuke and Itachi. We're currently on Orochimaru's fourth significant appearance (curse seal, Hokage fight, getting his arms healed, and now this fight against Kyuubi Naruto, and there'll be at least one more unless Sasuke pops up out of nowhere here). We've still got a good deal more of Sasuke and Itachi to deal with, a lot more Orochimaru to deal with (with Konoha, Sasuke, Naruto, and Akatsuki), Kyuubi taking over Naruto, Itachi vs. Naruto, various other members of Akatsuki including the superiors of the group (of which all the members we've seen so far seem to merely be subordinates of), Tobi, Kakashi's Mangekyo (possibly Gaiden 2, which we can expect since the first gaiden was numbered), and now Sai and Roots (along with any possible stories involving Konoha ninjas). But with all this, the whole first part (around five years of plot) can be summed up in three sentences:

Naruto was a runt with hidden powers, and he learns of these and grows, making friends on his way.
Sasuke wants revenge against his brother Itachi, and leaves Konoha for Orochimaru in order to obtain it, much to everyone else's chagrin, but especially Naruto's.
Itachi is part of a secret organisation that wants Naruto's power, which will be relevant later.

At this pace, it's really a bit of a pain to see new story elements be added, because it'll be at least another ten years before the whole thing finishes anyway, unless they've got the guts to accelerate the Sasuke/Orochimaru story so that Sasuke splits from him and goes after his brother, Naruto goes after Sasuke, Akatsuki goes after Naruto, and Orochimaru tries to out-manipulate them, re-joins Akatsuki (unlikely) or dies (really, Orochimaru dying would simplify the plot a whole lot - he's been presented as the big bad guy of the series, but so has Akatsuki, which causes problems for all that time we spent building up to Orochimaru being the big bad guy because him being defeated before the end will be a let-down no matter what, but so will cutting out Akatsuki from that, and since Akatsuki as a whole has been set up as having several times Orochimaru's power, having them be defeated first would simply be obnoxious). Roots needs to be forgotten in order for the story to not spin ridiculously out of control. If they try to tie up Roots, then add in at least another year of useless side plot, unless Roots ends up being related to Akatsuki, which might make it interesting.

Or they can cut the damn fight scenes down so that one battle doesn't take two months at minimum, and work on the story more. Then maybe it'll be finished in ten years even with all the extra plotlines (though I still expect a part 3 no matter what).