There's been some speculation that the storyline won't be quite a straight adaptation of the comic.
http://www.ign.com/articles/2015/05/20/7-things-marvel-cant-do-in-captain-america-civil-war?read
So it'll probably be a bit more small scale. Makes sense, we've seen several comic movies tackle comic storylines before, but there were many changes from the source material. Sometimes this works (X2/God Loves Man Kills, Days of Future past, Spider-man 2/Spider Man no more etc.) sometimes it doesn't (Spider-man 3, X men The Last Stand and it's attempt to mix the Dark Pheonix and cure storylines from the comics etc. Amazing Spider-Man 2 and Gwen etc.).