It's pretty obvious he's returning as a baby face, especially since he's returning in his home town of Chicago (no better way to begin a renewed face run than to start it off with the biggest reaction possible.) People always like to talk about how WWE doesn't always listen to it's audience and tries to force things on them and us who to cheer for and who to boo, so let's be consistent - there's no point in trying to make people hate Punk when audiences clearly want to cheer him. The guy got reactions during his entire heel run, even against The Rock.
I just hope he adopts his 'tweener' personality from the summer/fall of 2011 when he was knocking John Cena and The Rock and Triple H and owning Kevin Nash on the mic. Please no smiley dick baby face persona from 2012 that lost any sort of edginess he had from the summer of Punk. That period was when he was his most popular, which should be a sign of what worked best for Punk.