I haven't really followed the discussion here on anywhere else because I honestly feel pretty meh about it all. I somewhat enjoyed Fallout 3 as an exploration shooter but it has horrible writing and quest design and sub-par mechanics. I enjoyed Fallout NV a whole lot more and consider it the true Fallout sequel, although it suffered from a crappy engine. So, judging from Bethesda's previous entry and what a shitfest Skyrim turned out to be, I can't really say my hopes are high. That said, I will most likely give it a chance if not only to judge it by my own experience and crap on it legitimately.
As for the trailer, without reading any of the supposed leaks or any previous discussions, I have a hunch we'll play as an android and the turorial and character creation will take place pre-war. There's a "you're Special" book in the kids room in the beginning, and the pre-war footage seems to follow a young boy into the vault. It all is presented in a way to give a nod to how you started as a kid in Fallout 3. And since the trailer is supposed to be rendered in-game, I doubt all the assets for the pre-war footage would be there for the trailer only. That begs the question if we're an android from the very beginning, or if we're an android with the memories of a real person. And if we are indeed an android, we might have some more interesting perks, traits and other character upgrades available.
All-in-all, I'm most curious to see what Beth has learned from Obsidian. I would not be surprised if they're too stuck-up and prideful to not learn from their previous mistakes. I mean, NV was clearly not as successful as Fallout 3. Obviously Obsidian didn't know what they were doing.