THQ had announced plans for a big massive expansion pack for Saints Row: The Third titled "Enter the Dominatrix" which was planned to be released in late 2012. However due to time constraints and THQ's bankruptcy, it was later merged with Saints Row IV and made a full sequel.
The trivia items below may give away important plot points.
When Cyrus is giving the speech after the initial STAG attack, he mentions a girl named Jessica who was "kidnapped by a gangbanger, and crushed to death while he laughed." This is a nod to the previous game, where in a mission to take down the Brotherhood, you kidnap Jessica and throw her in a trunk, who later gets crushed at a monster truck derby by her boyfriend.