The Halo brand is a license to print money, and Microsoft has taken advantage of its cash cow by milking it for games, novels and comics. (You just know that a movie isn't too far off either)
But along the way, the company has maintained serious quality control as it has let Halo threads go off in various directions. The ideal next move between flagship games: a Cortana spin-off. Master Chief's blue-hued, artificial-intelligence-born companion might be a two-dimensional hologram, but her look, story, and fan base all have enough juice to propel her forward with a solo title. Use a tie-in title to dig deeper into Cortana's connection to Dr. Catherine Halsey and let Cortana play in and out of the boundaries of a Matrix-like universe.