Not really anything with any kind of source, but I think there is a very small possibility that the trailer showed us no name for a reason.
Halo for Xbox One is what we currently have. We know Halo is one, if not the biggest Xbox game. Then why would Microsoft just leave every other Halo games behind to stay with the 360? Even Halo 4, a relatively new game, is not going to be ported to the Xbox One. Apparently.
So I thought, when I saw the line “Your journey begins on Xbox One”, our journey isn’t going to begin… It actually started almost 12 years ago! So, without getting anybody’s hopes up, what if there is a really small chance that the trailer is not just a tease for an upcoming new story, but also it means past Halo games are going to be ported into the Xbox One? Would you be happy with this? Would you consider buying an Xbox One if this happened?
And, of course, I am not convinced this is true. If you have any arguments saying that this is completely not going happen, I am happy to listen and consider.