Cortana is not dead, and it is doubtful that the Didact is either. There were little things throughout the game. Someone mentioned it in the thread. There is a possibility that Cortana will be bought and transformed into a living being.

Possible Precursors in the future Halo games.

Masterchief was described in detail in one of the novels. I don't think it is a big deal that they revealed it.

Great game, great start for 343. Can't wait for the next one.

Yes I do, he was previously described anyway and seeing his face during childhood and during his augmentation just gives much to the story.s

I wouldn't count on precursors. 

You guys do realize the entire game you arent fighting forerunners right?

The Promethians are human beings that were transformed by The Conductor.

The Librarian tells that to Chief during the mission Reclaimer.

I loved the story! Cortana most likely will be brought back in Halo 5. That is most likely what it'll be about. Didect appears to be still alive as well from him talking at the end.