I have a few things to say here.
First, like many people have said, this is not a main event match. Regardless of what you want it to be and what WWE may say, unless they hype it more than other matches and put in on last, it's not main event.
Second, I can't believe how many people like the Miz. Maybe I'm in the minority here but I just do not find him amusing. Randy Orton is a heel that I see and think yeah I want to see him get beat, the Miz is a guy that I see and just think he's a legit dick and don't care about him. He's a decent wrestler, nothing special. He's ok on the mic, but I think there are certainly other who are better. And his look? He looks like a teenager going through an identity crisis. He wears like 50 things. It looks like he said "what's an interesting article of clothing from this subculture" and added that to his wardrobe. I am not not and likely never will be a fan of the Miz.
Third, this is really doesn't have much to do with this thread but I'll throw it in here. I don't view Cena a top top level guy (even though it's clear he is). I just do not view him on the Stone Cold/Hogan level that WWE wishes I would. In my view, him working with the Miz actually brings him down rather than bringing the Miz up. If fan terms, I cannot believe that the Miz has a legit shot against Cena and if he does, Cena looks weak to me. I'm sure I'm in the minority on this one as well, but those are my feelings.