According to a report I read on wrestlinginc.com today, originally reported by PWInsider.com, that the odds are heavily against Punk being there.
The report alleges that people spoke to CM Punk in Las Vegas this past weekend, while he was attending UFC 170, say he was really non-committal about his status with WWE and treated it as though it's something in his past and has moved on. So, take that for what it's worth.
The fact that he hasn't been outright buried on WWE television, or that WWE has yet to make any sort of address on Punk's status beyond Vince saying that he's on "sabbatical" prior to giving WWE's financial report for 2013 suggests that Punk isn't truly gone. However, I sincerely doubt Punk will be on the show in Chicago and, as a result, I think the best chance WWE has of taking some of the hostility out of them will be to produce a pretty hot show that features a lot of The Shield, Cesaro, Daniel Bryan, some others and do some hot follow up on The Undertaker vs. Brock Lesnar program.
There's gonna be CM Punk chants regardless and I don't think anyone really expects him to be there. I'm sure there are some hoping for the slim possibility to become reality, but I think that's as far as it goes. If they're willing to pay money to come to an event just to chant CM Punk all night knowing that there's probably better odds that Michael Jordan will come out of retirement to play for the Bulls than for Punk to show up, then let 'em. I won't be watching Raw to listen to/hear what they're chanting anyhow, so they'll be the ones looking like idiots chanting for a wrestler all night they're almost certain won't be there.