Several things to say about the trailer:
1. When MX mentioned about the keyblade wars and legend, something about the creation after destruction he wanted to know about the light in the legend. Here is something I just thought about right now; could that light be the same light, the door to light from KH2? I think this one is probably way off, but that is just mean.
2. I think pretty much if you can tell that Terra chose the Path to Darkness so he can control the darkness in his heart, I want to know why is he want to control the darkness? Ven chose the Path to Light, even though he follow to find Terra in seeking to control the darkness. Aqua chose the In-Between Path because well she went to seek both Terra and Ven because one, she sensed great danger if she don't find Terra and she is worried about Ven. The more reason is that if you noticed in the Jump trailer, she is front of Castle Oblivion, the main setting in KH Chain of Memories, which ten years later the Organization 13 used it for research center, and to look for Chamber of Awakenining.
3. The thrid thing to say is definately the same question we all asked since it begins, is there going to be Kingdom Hearts 3 or sequel for BBS. I think, yes there is going to be Kingdom Hearts 3 because in the Jump Trailer, Ansem the Wise said that the boy who can save the memories of the three or something like that, he was about to say "Sora's" name, Sora. Also, remember that this is 10 years ago before the first Kingdom Hearts which means during that time, Ansem the Wise was conducting the research about the hearts. His research about hearts caused it to lead the creation of Heartless, betrayel of his apprentice and banished him into the Realm of Nothingness, played an important role in the series during Chain of Memories, 358/2 Days, and later in KH2, and eventually he died in the World that Never Was when he was extracting the hearts from Xemnas's Kingdom Hearts.
BBS will answer all of our questiosn, theories, and more, but it will makes even more new question and theories after BBS. Let's just hope that will happen.