According to Variety, Disney will release another Star Wars film in between Episode VIII and Episode IX. Rumored to have a release date of May 25, 2018 the currently untitled anthology film will be based on Han Solo and will star Alden Ehrenreich as the Galactic smuggler. This is the second of the three films promised that are tied directly to Episode IV A New Hope which was released in 1977. No other cast members have been released and there is little information about the film. The film has to credited directors, Philip Lord and Christopher Miller.
The next movie, Rogue One is due out December 16 and also takes place before Episode IV and stars Felicity Jones.
This is how the Star Wars releases stack up.
Rogue On: December 16, 2016
Star Wars Episode VIII: December 15, 2017
untitled anthology film about Han Solo: May 25, 2018
Star Wars Episode IX: 2019
Disney Talk Blog 