I am really looking forward to this game now. The actual Persona dev team is in on the development as well, so this really is shaping up to be a true sequel. It looks like the only thing that is changing is the combat style while in palaces, which can be a good or bad thing. If they put a decent spin on the musou style to make it feel unique and deepen it a bit, this could really turn into something special.
In any case, my hype has been raised a good bit by this trailer!