Production on Episode IX is likely to begin this summer, so any casting information about the film should be dropping in the next few weeks. Here is the first one, and its a solid one. Keri Russell, probably best known for her role in The Americans is in talks to join Episode IX.
Russell has already worked with JJ Abrams on more than one occasion. She starred in a TV show called Felicity that JJ was involved in and she had a role in Mission Impossible III that JJ directed. Russell also had a role in Dawn of the Planet of the Apes.
According to Variety, there are still two roles that need to be filled before Episode IX begins production. Lucasfilm was interested in several actresses before settling on Russell prior to July 4th.