Brock Lesnar brought a lot of WWE fans with him to the UFC. When he went back, rest assured that some kept watching. And you can also rest assured that he took some MMA fans back to the pro wrestling world. CM Punk will likely have the same effect. Ronda Rousey will, if she keeps on showing up at WWE events. Believe it or not, the cross-over doesn't have to have a winner or loser: both pro wrestling and MMA can increase their fanbase by feeding off one another. The crossover can be best for business for both parties.