Between the Shadow War and the Civil War, there should be plenty to keep your players occupied through the end of Season Three and all of Season Four for a horde of game sessions, you just need to expand on the conflicts a little.
A lot happens off-screen during this time period. During the civil war, for example, you could base a large chunk of your game around the resistance movement on Earth itself, or focus on the liberation or secession of one of the colonies.