I made a theory about this a long time ago. I think it was my first theory. But now, this time, it is so close to being a confirmed fact that its somewhat scary. Thank to Jeane Uchiha for contributing.
About snake, crow and fox
The Crows and the Serpent Tale - The Crow and the Snake, Panchatantra Story the Trick of the Crow
sasuke = snake
itachi = crow
madara = fox
if he remain a snake, he will be fooled by the crow, that had the help of the fox;
About hawk and crow
(-:-) Bardo Surfer ® (-:-): Why crow fights hawk
sasuke = hawk
itachi = crow
mouse = sharingan
if he become a hawk, the crow will try to steal his mouse, and fight with him for that, but the hawk will end up with the mouse for him;
Its not the first time that Kishimoto would use the animals to represent the things, Sasuke x Orochimaru was the same thing:
Why sasuke will be a hawk in the end:
kishimoto planned the sasuke - snake - hawk thing a long time ago, the same way he planned about madara - fox - (probably a falcon in a little), he was always a hawk since the start, the problem is that the hawk still has the snake in his talons.(when kishimoto created madara, and the kyuubi attack, he probably thought about how would be his relaction with the plot, so he thought about sasuke/naruto);
Sasuke on a bird? Wow, how many coincidents can there be?
here is even funny, the title of the chapter 3 is uchiha sasuke, and the picture shows naruto with a bird at his side, using a bandage of konoha ¬¬'-
-in the 4th chapter he showed the team 7 - sannin thing, and how sasuke would go to the "snake" side-
What does become a hawk mean to sasuke:
He will win Itachi and get back/still have what Itachi took/tried to take from him, just like what happens when one hawk fight against a crow and get his mouse.
In the end, the hawk will win the crow and have his mouse, the same way the hawk got the snake in his talons
How will sasuke become the hawk that he always was?
Sasuke will have problems with Itachi until he figure out that he needs to become the hawk that he always was, back in konoha, he needs to figure out that he needs to return to konoha and his friends, that is what i believe, and he will think that in a little, probably he will figure out that he went to the snake side for "nothing", the gap between him and itachi will remain, and he will just stand up and fight when he remember and regret all what he did to his friends and konoha, when he figure out that cut his bonds never helped him and he will win itachi after that, when he fight because all the bad things that he did because of this revenge, not only because of this revenge.