What will happen if CM Punk walks out of WWE the WWE Champion?

Well, since CM Punk's contract expires after the Money in the Bank PPV, and he is in the main event against John Cena for the WWE title, what will happen if he leaves WWE as the WWE champion? Will he form a company feud? And if John Cena loses to Punk and gets fired, wont he go to the company that Punk will be in and get the championship from that company and bring it back to WWE?