SPOILERS: Don't read any further if you don't want to know:
Before I begin, I just want to say that I've been seeing this characters appearance in Guardians of the Galaxy plastered all over the internet, so I don't think it's a spoiler at this point. I just wanted to provide the fans who thought it was cool to see the character with information on how the character actually ended up in the film, and if we'll see him again.
George Lucas' Howard the Duck movie was the first Marvel film ever made, and an embarrassment. I actually tried watching the movie again recently, and I couldn't even get 30 minutes into it. Regardless of how bad the movie was though, he has still got the nostalgia thing going for him, and it was awesome to see him in Guardians. If anyone could make Howard work, it's Marvel and director James Gunn.
While talking to Empire, Gunn revealed how Howard came to be in the movie saying:
"I think it was some combination of me and the editor Fred Raskin who said, ‘Let’s put Howard The Duck in there. What if The Collector looks over and sees Howard The Duck sitting there?’ And I wrote down the line, ‘Whaddya let it lick you like that for? Gross.’ Fred and I thought it was hilarious, but we weren’t sure that (Head of Marvel Studios) Kevin Feige would go for it. But we told Kevin and Kevin couldn’t stop laughing, so that’s how it came about."
When asked about Howard the Duck possibly getting his own movie, Gunn replied:
"I’ll be honest with you, I was just talking about it with my assistant right now (Laughs). It’s possible Howard could reappear as more of a character in the Marvel Universe. But if people think that’s going to lead to a Howard The Duck movie, that’s probably not going to happen in the next four years. Who knows after that?"
I don't think the character needs his own film, but it would be cool to see him pop up every now and then. In a separate interview with CBR, Kevin Feige talked about Howard's cameo as well, saying:
"I think it would be fun to lay claim to Howard and to remind people that he’s more than just a pseudonym for film failure. And that he is a Marvel character. That would be fun."
Feige then went on to talk about the famous Disney lawsuit threat that forced Marvel to give Howard a different character design and wear pants so that he didn't look like Donald Duck:
"And no legal wrangling over pants with Disney this time! No. I wasn’t even aware of all that stuff until recently!"