Sins of a Solar Empire: Rebellion is the third expansion to the original game and is coming out as a standalone game. It adds additional things to the game, including new factions, capital ships, variations on old ships, a giant new class called the Titan class and some new small corvette class ships. What is the rebellion? See below.
The time of Diplomacy is over. The length of the war and differing opinions on what should be done to bring the war to an end has led to a splintering of the groups involved. The controlling powers-that-be have depleted arsenals and seemed to have exhausted all efforts of diplomacy. Trapped in a stalemate, sub-factions have rebelled and broken off the main alignments. Rebellion is upon us.
Check out the newly released teaser trailer for the game below. It looks pretty freaking awesome!