On that topic, I wonder how 343 will advertise the next game based on what know about the end of 4.
If Cortana is coming back will they have to put her presence in the trailers? What about the Didact?

I'm thinking if they plan to have the Didact come back, he will have to be in the advertisements. If not they will have to invent a new enemy and present that in the trailers much like they did with Halo 2.

But Cortana, now that's a weird case. They may want to keep her return a secret and not let us see her until we play that game. But if she is going to be as big a character as I imagine she would be, how could they get around that? Interesting...