I never liked the Halo 3 terminals, to be honest.

They were fun to find, but I really didn't like the fleshing out of the Forerunners and preferred them to remain mysterious and interesting. Part of my reason for my immense dislike of Halo 4 was taking away all that mystery and shoving it in our faces.

If you're going to make characters from terminals into the primary protagonist and antagonist of a sequel, at the very least do NOT toss out the prime material and make two versions of a character so he can be an angry monologing kitty.