As many of you are aware Agent Coulson is a character in the Avengers film universe. He is not an original character taken from the comics and has appeared in both Iron Man films, Thor and is to appear in the Avengers.
Now here are the things we know about Agent Coulson. His name is Phil Coulson. He is an agent of S.H.I.E.L.D and he was a recruiter on the Avenger Initiative. However there have been some speculation on a few things. First, people have been hearing the rumors that the Skrulls may be in the Avengers and he may even be one. Personally I hope he's not a Skrull but that's just me.
Secondly people have been thinking about his position and attitude and think he may be a well known Avenger himself. Yes, it has been rumored that Agent Coulson may in fact be the Vision in disguise. I think this would be amazing however let me put these rumors to rest. In Thor Agent Coulson encounters the Destroyer which attacks him and a few other S.H.I.E.L.D agents out in the desert and he did not turn into the Vision then to save the day so this leads me to believe he is not the Vision.
But his character does share the Vision's calculating attitude and I believe (and this is just a guess)that he will have his conciousness restored in the Vision android body after he is killed. Thus adding a great character while keeping the old one. Then again we could all be making something out of nothing and Agent Coulson could just be a regular, old S.H.I.E.L.D agent.
Joss Whedon also gave information that states that the Vision will be hinted at in the Avengers along with Black Panther and may appear in an Avengers sequal. Whedon also went onto say that if they do make the Vision appear in a sequal he will be created by Tony Stark and a group of scientists, not Ultron. Please remember I am only the pervaier of news with the slight additon of my opinion.