Basically, you play as CM Punk through the standard Career Mode/Universe Mode/whatever it's going to be. Every week, you get an option to "Walk". If you don't, you get a "Congratulations" screen and a really fucked up storyline unfolds for you to partake in. This is your "Thanks for not Quitting". You make it through this said scenario, you unlock something (Extra stuff in Create Modes). Then you're back to Career/Universe Mode. Only now, the controls have changed and you start struggling in matches and lose some big matches you'd think CM Punk would win. Now, the option to "Walk" is in the normal menu screen and can be used at any time.
Should you choose "Walk", CM Punk is gone and you get to choose someone else to use. Once in awhile, you get a cutscene to CM Punk at home and you get the option to "Come Back". A mini-Game pops up and this decides whether you come back as a monster face or as a pissed off, self-loathing, "I didn't have anymore money and HAD to come back" type character. Then it's back to Career Mode/Universe with CM Punk if you chose to have him come back, then more screwed up scenarios and options to "Walk" again.
Romors of a "Hot Coffee" scenario with AJ Lee have been scrapped, as of this writing.