If ADR was going to get added to the title match by Vince, it would've already happened tonight.
I can see 3 scenarios happening.
Del Rio wins MITB, Punk wins the title, and Vince comes out to fire Cena and just as Vince is getting the YOOOOOOUUUURRRRREEEE part of his you're fired phrase out, Del Rio's music hits, he comes down with the briefcase and cashes in on Punk, thus Cena keeps his job.
or
Del Rio is taken out of the MITB match. Vince McMahon does something such as give him the night off, or whatever, and promise him the next #1 contender opportunity. Punk wins and Vince announces that Del Rio's previously earned #1 contendership is still valid, so he comes down and gets a MITB style match right then and there, ala Batista in 2010. This allows the WWE to give Alex Riley the MITB instead, and build him up with it for a long time instead of wasting the contract on Del Rio when he's got another easy path to the title.
or
Vince screws Cena out of the title and raises Punk's hand, leaving everybody confused and eager to turn into Raw tomorrow night, where we find out that this entire Punk leaving situation was an elaborate charade designed by him and Vince to screw Cena out of the title and Punk already signed to a new deal. Cena is fired but he manages to fight it and come back like he always does, leading to a SummerSlam program where he wins it back.
Either way, I'm convinced now that Punk is winning the title because when I listened to Vince, I made sure to take close note of the wording. He didn't say "if Punk wins you're fired", he said "if Punk walks out of Chicago with the championship you're fired". So something is up. Cena can't just win and nothing happen, not after they've put so much detail in this angle, not after Vince showed up in person to have a long, great promo with Cena. We're past that.