This would be a JUICY totally BEYOND EPIC story for Halo 4. I'm like so eager for this game! Now, occording to your evidence, Prehistoric Humanity was evil, forunners beat them, And punished them for their acts by de-evolving them. Well, that cutscene could be with the purple guy is someone from prehistoric Humanity. Coming on an act for revenge. The blue guy, a forunner defending against "PH" (prehistoric Humanity). PH is totally angry and vengeful. Other orange Scout Guy leads to an even bigger hint.
The Forunners need help and have to bring back De- Evolved Humanity. Considering the horrifying things things PH could do to the universe. PH uses his powers and finds one of De-Evolved Humanity and the cutscene ends there. Hmmmmmmm.... But even I don't believe myself