In an interview with Collider, the actor says “It’s essentially the fall of the last city the last stand of Manhattan. The movie would be…within the body of the movie D.C. and then Manhattan would fall as the last city. It’s a really cool idea trying to figure it out…there’s a reason why we have to take a small band and we have to get into D.C. So we have to make our way from New York to D.C. and then back to New York.”
He says they’re still working out the narrative kinks. And it will indeed be a prequel, not a sequel as was recently reported elsewhere on the web.