Lucasfilm recently pushed Star Wars: Episode IX to December and as a result has bumped the start of production back to June 2018.
Variety reported that Disney has made the decision to push production from an early 2018 start, now putting the film into production in June of 2018.
For the replacement, Lucasfilm went back to the man that started the Star Wars renaissance by bringing Star Wars: The Force Awakens director J.J. Abrams back to close out the trilogy.
He was reportedly being too difficult during the pre-production process, causing a rift between he and Lucasfilm president Kathleen Kennedy.