Saying that they need to clarify if this is the game they were teasing makes it sound like it isn't big news. SaGa is huge and we haven't had a new (non-remake) entry in the series for years and years.
Anyway, for people who don't know it used to be Squares biggest series after final fantasy, but most entries didn't get released in English. It generally has non-linear storytelling and a complex battle system that is like a more refined/advanced FF2. You pick which character to be the protagonist and follow their story. The games are generally very hard compared to most JRPGs-- it's been compared to Dark Souls etc but I haven't played those games to say if it's a fair comparison. But because of the learning curve a lot of people can't get through them.
Also, it has a lot of the greatest battle themes I've ever heard in video games. Look up Kenji Ito's Re:Birth series.