The most notable plot development of the Civil War comic is that Captain America is assassinated at the end by Crossbones and a hypnotised Sharon Carter, leading to Bucky Barnes eventually taking up the Captain America mantle. This is a dramatic staple of modern Marvel comics and something that many fans will be eager to see play out given its grand cinematic potential. Furthermore, considering that Chris Evans is reportedly keen to leave the MCU when his contract is up in order to pursue a movie directing career, it almost makes too much sense... So yeah, it's probably best to prepare yourself for this one now. Bring tissues.