[Your favorite covey species that you wish will return in halo 4]

Brutes for the being the biggest extraterrestrial monkeys that would always find a way to hit me with there hammer

[Why the Didact will be a Good Guy in Halo 4]

Yes finally someone that will think thedidact will be the good guy I for one thinks its the master builder

one reason it might not be Faber(masterbuilder) whose last known location was on installation 07 and was possibly believed to have died, i agree with OP though i do think the Didact will play a role as an ally or a guide throughout the game