Michael Rooker talked a bit about why he's so likable and what his Yondu is like:
I don't know why, I don't know how, but it seems like I can be a real — dick! And people still like me. It seems like I have this little knack, so he sort of wrote that with Yondu in mind and myself in mind, this ability to sort of be abusive verbally, or whatever. [Laughs] Even physically, and still have the audience forgive and enjoy what's going on on-screen, and like it enough that they don't really care if you're really not a nice person. Yondu's not a nice guy, but he's got this paternal instinct, and it came like the first moment he saw Star-Lord. Got him up in his ship, and all of a sudden, the kid is, in my mind, this kind of little guy who's not all sheepish — he's just lost his mom, and he's still being tough, he's standing up for himself. That and maybe something else was involved that convinced Yondu to basically keep the kid. I kept him. Raised him as my own, as opposed to sending him off to where we're supposed to take him. And so there's that heart in there. I think people, they see through all the makeup and all the wardrobe, and they see the real person somewhere.
[Comic Book Resources]
James Gunn is already thinking ahead to the next movie, telling The Walll Street Journal about Guardians of the Galaxy 2:
"I have a good idea. Frankly, it's more important that the story works by itself than by how it fits into 'The Avengers.'" He has to keep certain things in mind to connect to the overriding story arc, but, "first and foremost, I'm concerned with the Marvel cosmic side of things and these characters."