In an interview with GameReactor, Assassin's Creed IV: Black Flag lead designer Jean-Sebastien Decant promised that the next game in the franchise would be "much more on the next-gen side."
He described Black Flag as being "on the edge," as it was developed before the next-gen systems were released. When Ubisoft began working on the title, they had no idea what the system specs would be for the Xbox One or Playstation 4, making development more geared towards current generation.
Decant also discussed the possibility of a more multiplayer-focused sequel: "I think we're going toward a gaming place where the open world will be shared with other players. More and more. Socially speaking, but also maybe multiplayer stuff. And we will have to consider the open world much more like a platform that we could sustain for years."
Ubisoft has yet to officially announce a new Assassin's Creed title, but given that a new entry for the series has been released every year since 2009, it is extremely likely that a new installment is in the works.