Ryokutya has reported from the latest Dengeki PlayStation magazine that The Legend of Heroes: Trails of Cold Steel IV -The End of Saga- will be released in Japan on September 27, 2018. This title will serve as a grand conclusion that wraps up all of the current arcs in Nihon Falcom's Trails RPG series. It will have a bigger volume and a lot more playable characters than Trails of Cold Steel III.
Trails of Cold Steel IV continues directly after the events of Trails of Cold Steel III, which was released last year in Japan. Unfortunately, no localization announcement has been made for either the third or fourth game. The first two Cold Steel games are currently available in English on PlayStation 3, Vita, and Steam.
Meanwhile, Trails of Cold Steel I and II also received PlayStation 4 remasters in Japan which were recently released as Trails of Cold Steel I -Thors Military Academy 1024- on March 8 and Trails of Cold Steel II -The Erebonian Civil War- on April 26 respectively. Neither of them has an English release announced either.
You can read our reveal article of Trails of Cold Steel IV, but please be advised that it contains spoilers through the end of Cold Steel III.