Homefront: The Revolution came out in May to something other than universal acclaim. It wasn't necessarily bad, just dull, although it suffered from technical issues too. A performance patch released at the beginning of September (hopefully) addressed the worst of the bugs, and now the first singleplayer DLC is live, to (hopefully) make the guerrilla war against the North Korean invaders a little more interesting.
The Voice of Freedom sets players up as Benjamin Walker, “hero of the Resistance and the most wanted man in America,” who's out to infiltrate Philadelphia and ignite a revolution that will sweep the KPA out of America on a tide of bloody vengeance.” Along the way, you'll encounter Jack Parrish's resistance cell from before the events of Homefront: The Revolution, and run up against a dangerous street gang in the Philadelphia subways called the “90.”
I could be wrong, but that description suggests to me that your mission to kickstart the revolution does not go well. America is still very much struggling under the Nork boot in Homefront: The Revolution, so if this mission takes place prior to that, it can't have ended well, right?
The Voice of Freedom is included with the Homefront: The Revolution season pass, or can be purchased separately for $6/£5 on Steam. Deep Silver also announced that new outfits for the game's Resistance Mode, including an Urban Combat Outfit, a Black and White mask, a Gunshot mask, and a Cobweb mask, will be released on September 30.