Chief's nemesis: The Didact?

All clues are leading up to this. In recent news, it is told that chief will have a nemesis in halo 4, and it all makes sense with the new clues. In the final terminal in CEA, they hinted the didact would return. In the halo 4 cinematic trailer, his symbol is shown on the computers. At the end of the trailer, it shows his symbol (again) with a voice saying, “I have dreamt of this day reclaimer”, which chief is probably the most notable reclaimer. only forerunners (and their tech) called humans reclaimers, there has to be some connection. Not to mention the big ball in the trailer is almost certainly a cryptum, which has obvious ties with the didact. But this raises questions. Why would the didact be evil? What does he want with chief and humanity? What are his motives? Any thoughts?

EDIT: For all of you who haven’t seen the latest news,

All evidence suggests that the didact will be the ancient evil although the symbol shown in the trailer and the symbol shown in past halo games and other media are slightly different

I honestly don’t understand why people keep making speculations like, I mean even if the didact was the chief’s nemesis would you actually want to know? seriously guys you’re kind of ruining the game for yourselves.

I’m sure we will be surprised, though, because the didact truthfully isn’t evil, so that rules out “the ancient evil” part

I’m still sticking with my theory about the Didact only being a “enemy” for a duration of Halo 4. The precursors HAVE to have something to do with the new trilogy, no doubt about it, due to the Forerunner Saga. I mean think about it. They’ve been hinting about the Didact for quite a long time. It can’t be that easy, can it? There’s more than the Didact, there has to be. 343 is good at hiding things.

I still don’t think the Didact will be an enemy at all; the Precursors are my candidate for Ancient Evil.

Never thought of that, but it makes a lot of sense. Wait, just so that I know, did the precursors invent the flood?