A new, very sparse, site has cropped up called "Devil Inside You" along with a quote that says, "In the shadow's dying light let the devils guide our fight". But what is of particular note is the Glyph symbol in the URL bar or on the site tab. Glyph, for those who do not know, is the launch platform for all of Trion's games.
We're digging around and will keep you posted!
In fact, Trion has tweeted the news themselves. We'll see what happens.
UPDATE: User Darthem pointed out a video for a game called Devilian Online, and so we found their current Thai website. Does the guy in the below screen capture from said site look familiar when compared to the Trion teaser site? Good call, Darthem. It seems we'll know soon enough if it is Devilian Online.