I was also wondering about that guy on the horse(which amazingly enough look like the horses from Suikoden 1 - Gulhorses?) I didn't know if she said brother or father. My japanese is far from great.
Th girl (forgot her name) said "father" in that scene. Suikox.com has a translated version of the trailer on it's main page.
Yeah, new areas of old islands and dungeons will be opened up it seems. For instance, thanks to SARS for the translation, we can see that one of the battles will take place in the Ruins of Obel, except in a new chamber.
I also saw a new location. I think it was some kind of town called the "Rural town Haruna". Which is good so it gives us more locations in the Suiko 4/Rhapsodia world. This game is looking promising.