Sting is one of the biggest names in the industry, and represents a huge match for anyone on the WWE roster. One of the reasons that Punk left was because he wasn't getting to work with the top, top stars. If he was offered Sting, it'd be more akin to the level of WrestleMania match he'd desire. As for Sting, working with Punk is the opportunity to have a really good match, which is a challenge for any wrestler north of fifty. Fans would want to see this bout based on the iconic status of both men. The dream scenario would be Punk in his killer heel mode, going after Sting the veteran babyface.