If Punk cashes it in to make a fatal 4-way there is no way in hell anyone but Edge is winning. That kind of match Edge is king. Because he can predictably play dead for 20 minutes while Umaga and the faces beat each other up, and at the last moment spear Punk and win. So it would be a waste of MITB.
The real smart thing for someone like Punk who does not look believable as a challenger is to cash it in post match and win it. It won't be against Orton, because then you have two titles on one brand again. And if its against Edge, its gonna be after the Jeff Hardy match as Hardy is already #1 contender and Punk is gonna be in a singles match against Umaga. If he doesn't cash it in on Judgement Day, I think the WWE would of missed a huge overness opportunity for Punk. Because they are not gonna get this perfect of a scenario again.