The "Star Wars" prequels may not be as popular as other sequels due to the extensive transfers of intergalactic politics and magic - but it has been proven to work with the high-ranking movie materials. I can be expected in the new movie film that the origin of the rebellion will be traced from the earlier Separatists time that started Clone Wars.
"Star Wars": Catalyst - A Rogue One Story," the new novel by James Luceno, starts right after the introduction of The Clone Wars. Then emergence of Galen Erso (Mads Mikkelsen) along with other characters are added after the war in the new movie. The rebellion came from the part of the galaxy where Separatists were fighting with the Republic, according to Cinema Blend.
The rebellion intensified only after the promises were not delivered to the Separatists. The Political details of this instance seem to match with that of the "Star Wars" prequels. Fans would know that Darth Sidious/Emperor Palpatine is responsible for the plot to establish the Galactic Empire.
He and Count Dooku stir up the conflicts in the Outer Rim and provide the Separatists droid army to go against the clone Army of the Republic. This means that Palpatine stages his own rebellion which destroys him in the end.
The Separatists have no clue with Palpatine's strategy. They blame the Republic for taking advantage of them and not sending their voice to the Senate. As soon as the Clone Wars are over, they discover the truth that they have no say at all as far as the Empire is concerned.
If the connection is right, the rebellion makes a major strike to topple the Empire just after implementing the Death Star plans. The story line will be much clearer when Rogue One: A "Star Wars" Story hits the theaters on Dec. 16, confirmed IMDB.