Oh -- an addendum to my last post:

If you're trying to remain relatively spoiler-free for Serenity, I'd recommend NOT going through the trailer frame-by-frame and trying to analyze stuff. The trailer actually gives away quite a lot, some of which I don't think I would have wanted to know going in. I know the wait is agonizing, and Joss has just tossed you one heck of a crumb, but if you want to do yourself a favor, you won't try to dissect it too thoroughly.