One rumor going around is that the Federation finds Khans ship the 'Botany Bay'. Spock 'prime' already knows what could happen and it is decided that Khan must die. Cumberbatch is Khan's second in command and seeks vengeance.
Again... just a theory.
The Chiefs will finish 5-11, Alex Smith will play horribly, and Geno and I will cackle with glee while he burns Kansas City.