1. He Wasn't A Major Part of Any Marvel Movie Before The Avengers
I don't feel like Hawkeye will ever get his own movie. He seems from the beginning a supporting character, the kind of hero who will stand outside the group and help during dire circumstances, like blowing up a certain shaft or shooting down a fleet of aliens before they get to The Avengers. But if he does, it will no doubt be a companion piece between him and Black Widow, which I have to admit would be very interesting. The duos back story is hinted at in The Avengers, enough to spark interest for a feature-length film. Hawkeye, being introduced for the first time in The Avengers , really had to take on the weight of being a mindless, but focused victim of the villain. It's too bad, I mean think about it: would Captain America still be cool if he had been a blue-eyed minion of Loki? We'll yeah, probably, and Loki would have spray-painted over the blue in his suit and made it black, I would think. So I hope you realize that Hawkeye wasn't set-up to be liked: he was meant as a plot point, and hopefully in the next movie we can see more of a character in him, and maybe a little romance between him and Natasha, too