Since its beginnings, Naruto has developed over several different storylines - some interconnected, some seemingly incongruous. However, through each storyline a basic structure is followed. Good is pitched against evil - a 'big, bad guy' inevitably emerges.
Orochimaru emerged relatively quickly as the arch-nemesis, but as the Manga progressed, Itachi stole the show and has continued to dominate. Until now, both of these characters have been allowed to develop - and have been shown to be equally powerful.

And my speculation rests upon this: how will these two characters interact? How will the story develop around them both?

It seems inevitable that Sasuke will eventually face up to his brother. Perhaps he will fight for Orochimaru? This would potentially lead to agression between Itachi and Orochimaru.

Will Itachi be killed by his brother, or redeemed in some way? This too is unclear.

Of course, Naruto is the principal character in the series - it being named after him.
Therefore, it is certain that he will also face an ultimate nemesis. Is this nemesis necessarily to be found in Orochimaru? I am not sure. I think Kabuto (or perhaps Sasuke) may well kill his master - this would be ironic considering that Orochimaru killed the Hokage.

If Itachi is killed by his brother the final showdown could be between Naruto and Sasuke.

Yet I anticipate that Naruto will finally face Kyubi. I do not know how he will beat him - but the demon fox appears (imo) to be his greatest adversary.

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This is really just a collection of thoughts about the development of the series which will, I think, be propelled forward by the 'bad guys'.

Comments?