Sure, sounds plausible. Only problem I have with it is the fact that the Didact seemed to feel sympathy (or rather something more close to respect) for humans. I could accept your version as the storyline though, as the books Halo Cryptum and Halo Primordium left a lot of room to change the plot and characters. For sure there will be a great twist as Greg Bear himself said something along the lines of, "for strategic plot reason Halo Silentium (next book in the series) will be released after Halo 4", so there is no doubt that the book will explain the twist that Halo 4 will undergo.
Personally, I took pre-cursors being a "God-like" creature figuratively and believe they will be the next antagonist. After all the timeless one did state, " Once I die another will come to take my place". I am sure I will probably be proved wrong later when the game actually comes out.
Another twist which I thought that maybe could support your point is that Greg Bear did say for Halo Silentium, " Let's just say that there are two Didacts", but until the next book comes out next January I can only hypothesize what is in store, but with two of them there is more room for an evil one I guess.
(P.S. sorry if I repeated what others have said but I have only read the first and last post)
