Akitoshi Kawazu, creator of SaGa 2015, this week revealed a handful of details to Japanese outlet Famitsu regarding the upcoming Vita RPG, including non-linear gameplay and multiple heroes. Kawazu doesn't consider the game a true sequel to other SaGa games though, based on various differences. He did name the character seen in early concept art - "Firebringer," and said the setting is reminiscent of Romancing SaGa.
It's not much to go on, but hey...