In fact the director of Step Brothers, The Big Short, Vice, and Anchorman Adam McKay was actually approached by Disney for a possible collaboration. According to McKay, “We’ve talked a little bit. We were kicking around the idea of The Inhumans at one point. We’re always kind of talking. I think [Kevin] Feige is just the greatest, and I think what they’re doing over there is amazing.”
Unfortunately McKay did not mention whether or not he might have taken the role, or if his conversation was more informal and was nothing more than just shop talk, so for now it is still very much up in the air as to who will be directing the third installment in the Guardians of the Galaxy franchise. However at the very least we know that McKay could be one of them.
At the same time even if he weren’t to direct the movie, McKay has expressed interest in possibly working on other Marvel characters, such as Silver Surfer. With the Fox acquisition already underway, it would bring Fantastic Four back under Marvel’s ownership, which means that a possible Silver Surfer movie that exists part of the MCU is a possibility. Whether or not that happens remains to be seen.