Okay, I did not originally form this idea because of assassins creed, I’ve never actually played the games (though I am aware of their general plot), but after thinking about them, I noticed the parallels.
This idea came about more because of the focus on bornstellar receiving the didacts memories throughout cryptum. Also, recent interviews and events have hinted at their being a strong connection between current fiction and the game, particularly Greg Bears novels. In a recent interview I believe it was Frankie who said Halo 4 will act as a prequel to halo fans.
Prequel, yet it takes place after Halo 3?
So my thoughts are this. Chief “lands”, wherever that may be, whoever may be there. He seeks out these terminal like structures. There he is given didacts memories. We physically inhabit the didact, and play as him. We play through his memories: we get to inhabit a forerunner combat skin, use forerunner weaponry, see the forerunner empire as it existed and fell. Half of the gameplay consists of us playing through didacts memories, and half consists of chief, in real time, seeking out these terminals and dealing with the threats where he lands.
The enemies we are fighting in the current time I feel will be revealed to us through the forerunner trilogy. The primordium description hints at there being a creature that created the flood (called Primordial). Also, it seems to imply that the precursors and the forerunner were at odds. As chief receives more of didacts memories, he of course learns how to use forerunner technology, so he will gradually be able to use forerunner weapons and maybe even a forerunner combat skin.
By the end of the trilogy, John now has all of didacts memories. If you’ve read cryptum, perhaps you could understand that John would become the new didact. The first didact of the new bearers of the mantle: humanity. At the end, after defeating the ancient evil, the mantle is officially handed over to humanity. All the knowledge and technology the forerunner have accumulated are passed on to humanity. John takes all this and returns home to Earth in a forerunner ship. Karen travis’ new trilogy is set to explore the state the galaxy is in following Halo 3. What if her trilogy set up the galaxy to be in complete shambles, broken and disconnected following the human-covenant-flood war. Master chief would be returning from his ordeals to a war torn galaxy, to fix it, the galaxies saviour. Ending the story of halo on a hopeful note.
Observation: The very last scene in Halo: Reach takes place during the year 2589 (I think?). Notice that Reach has gone from a dead ball of flame to a completely life bearing world in 30~ years? It could not do that naturally. The forerunner were known to create planets. If humanity had forerunner technology (that chief brought back with him), they could easily re-terraform Reach. If you look in the distance, to the left, you can see what resembles a ship of sorts. It looks like no human ship we know of. But 30 years from 2553, humanity will have integrated forerunner technology into their own (if my general theory is true). That ship could be a new human vessel, bristling with technology passed down by the forerunners. The ship does not look that different from the smaller craft on the cover of primordium.
Something else to consider: From the new description of primordium on amazon, it seems chakas is talking to someone (the chief?). I suppose it is equally viable that the chief receives chakas’ memories rather than didacts.
This is a very loose theory, trying to perhaps explain some very general plot points.