The name Brigandine: Lunasia Senki was recently trademarked by Happinet Games in Japan. At the time news of the trademark was posted, Gemastu discovered a placeholder website at brigandine.happinet-games.com.
Today, that placeholder website has updated, and while it is still blank, the title of the page is now “Brigandine: Lunasia Senki,” and the source code contains the following image and description intended for social media link previews:
The endless battlefield fantasy, country-takeover simulation game Brigandine: Lunasia Senki will be released for Nintendo Switch as a completely new title by new developers!
Brigandine is a tactical RPG released for PlayStation in April 1998, which was followed up by a remake featuring multiplayer support and many other significant changes in May 2000 called Brigandine: Grand Edition. While the original game was localized by Atlus U.S.A. for North America, Brigandine: Grand Edition was never released outside of Japan.
Happinet Games will have a booth at Tokyo Game Show 2019, which runs from September 12 to 15 at the Makuhari Messe in Chiba, Japan. It is likely that Brigandine: Lunasia Senki will be announced in the lead up to the show, or at the show itself.
Update 08/24/19 at 1:30 a.m.: As noted in the comments, there is also a PlayStation 4 logo image uploaded to the website. However, neither the description of the website mentioned nor the error page displayed the PlayStation 4 logo, so whether Brigandine: Lunasia Senki is coming to PlayStation 4 is still unknown.