I'm surprised the question was even asked (did we not see Episode IV?), but Disney has made it known there will not be a Star Wars: Rogue One sequel.
Disney's Kathleen Kennedy made it be known in the latest issue of Empire Magazine (via slashfilm) that no matter how well Star Wars: Rogue One performs at the box office, there will be no sequel. Rogue One director Gareth Edwards and the Lucasfilm chief creative officer and former visual effects supervisor who came up with the idea for the movie in the first place, John Knoll, confirmed no Rogue One sequel as well.
Edwards even mentioned that the sequel to Star Wars: Rogue One is Star Wars: Episode IV – A New Hope by referencing any sequel to Rogue One will be directed by George Lucas.
While the the box office of Star Wars: Rogue One will not affect the probability of a sequel, Disney is keeping an eye on how well Star Wars: Rogue One performs in deciding future standalone movies. Obviously if Star Wars: Rogue One is a smash hit, expect further standalone films, of which Han Solo is currently in development.
"Star Wars: Rogue One" has a December 16, 2016 release directed by Gareth Edwards and stars Felicity Jones, Diego Luna, Ben Mendelsohn, Donnie Yen, Mads Mikkelsen, Alan Tudyk, Riz Ahmed, with Jiang Wen and Forest Whitaker. Kathleen Kennedy, Allison Shearmur and Simon Emanuel are producing, with John Knoll and Jason McGatlin serving as executive producers.
Synopsis:
From Lucasfilm comes the first of the Star Wars standalone films, Rogue One: A Star Wars Story, an all-new epic adventure. In a time of conflict, a group of unlikely heroes band together on a mission to steal the plans to the Death Star, the Empire’s ultimate weapon of destruction. This key event in the Star Wars timeline brings together ordinary people who choose to do extraordinary things, and in doing so, become part of something greater than themselves.
Star Wars: Rogue One trailer: